Issue #2709557: X-PROPERTIES now import properly when added via hook_date_ical_mapping_sources_alter.

I used to like keeping whitespace on blank lines that lined up with the
indentiation level of the code. I don't like doing that any more, so out it goes.

Thanks go to d.o user MegaChriz for this fix!

Because the iCal spec states that VFREEBUSY components can't have the
SUMMARY property, Date iCal will now fall back to the COMMENT property
for the node title. Unfortuantely, this is the best we can do, becaise
iCalcreator completely leaves out the SUMMARY property on VFREEBUSY
componeents, so there's no way to recover it.

Thanks go to user mgalman for the patch!

iCalcreator knows that certain iCal properties (e.g. ATTENDEE) can have
multiple entries in a single VEVENT. So when you access ATTENDEE for the
first time, it gives you the first entry. Accessing it a second time gives
back the second entry, or at least it tries to. If there is no second
entry, iCalcreator returns False.

Since Date iCal does not yet support multi-entry properties, I had to work
around this functionality to ensure that hooks which add custom mappings
don't run afoul of this process.

Thank you t0xicCode for this patch!

There's a new setting on the "iCal parser" settings page, which lets you set
an integer number of days. Events which ended more than that number of days
before the import will be skipped.

Date iCal doesn't currently use this new mechanism (I originally created it
for a feature that ultimately didn't end up needing it), but it may be
helpful in the future for when one handler needs to know about the results
from a previous handler's pass over the same event.

All day events which start on the last day of a month and don't have an end
date specified were broken, due to a silly mistake I made in the DTEND
emulation.

This hook allows modules to alter the final data array for each event,
just before it gets sent through the rest of the Feeds processing steps to
be turned into a node. The context array is what separates this hook's
functionality from what users can do with Feeds Tamper.

By using the amazing, free database of Windows timezone names curtesy of the
CLDR project (http://cldr.unicode.org), I was able to add support for the
non-standard timezone names created by Microsoft Outlook. Hopefully, the
"not a valid timezone" error will now be much less common.

The Date Repeat module’s date_repeat_build_dates() function does not support
RDATEs and EXDATEs defined as separate properties, as well as being a bit
buggy in other ways. So I copy-pasta’d it and made the necessary fixes.

I wanted to add support for EXRULEs, but it’s more complicated than I
expected. So since no one has actually asked for it, I left it as a TODO.

As jakemonO pointed out, the Calendar will not display All Day events which have no
end date value, which means that Date iCal's method of leaving off the end date for
single-day All Day events was a really bad idea. Fortuantely, setting the end date
to the same day as the start date makes the date node display correctly for single-
day events, which was the reason that the end date was being left off in the first
place. This means that every All Day event can simply have it's end date rewound by
one day, and all is well in both the node display and the Calendar.

Renamed hook_date_ical_import_calendar_alter to hook_date_ical_import_vcalendar_alter, to match the export hook.

Also did some minor refactoring and comment editing.

Date iCal 3.0 is nearing completion! The only major task remaining
is to write the migration code.

iCal feeds are now parsed in batches of 50 (by default).

The Date parser code has been significantly improved, removing the
old limitation of needing to parse DTSTART first, and also covering
more edge cases and error conditions.

I hadn't yet tested the RRULE import code when I first pushed Date iCal 3.x-dev,
but now I have. It's much more robust than it was in 2.x.

In addition, I moved the parsing class out of DateiCalFeedsParser.inc and into
libaries/ParserVcalendar.inc, which is like how Feeds' own CSV parser is set up.

This new version is still in a state of partial completeness. You may need to do
some manual fixing to get it working, due to a change I made in the classes
offered by this module. Try 'drush cc registry' if 'drush cc all' fails.

Please note that ALL of the hooks exposed by Date iCal have changed. They do
essentially the same things they used to do, but they're named differently.

The big change is that the Feeds plugin has been completely re-written to
conform to the Feeds APIs. It's now much more resilient and powerful. Feeds
Tamper will now work, and is in fact the prescribed way to alter data, since I
removed several alter hooks.

Issues [#1931020] and [#1935820]: Allow custom fields for summary. Fix repeating events causing duplicates. Add @file to DateIcalFeedsParser.inc

Applied patch #11 from [#1922658] to get around iCalcreator limitation with stream wrappers. Also made the amount of whitespace on blank lines consistent throughout the project.

Includes patches from issues 1895396 and 1462646.
Updated the README and the CHANGELOG.