drop RT 3 support

in the future, we migrate js/css files to RT 4's structure.

MANIFEST

 Changes
-etc/jsgantt-showsummary.diff
 etc/jsgantt.diff
 html/Callbacks/JSGantt/Elements/Header/Head
 html/Callbacks/JSGantt/Elements/Tabs/Privileged

README

@@ -37,11 +37,8 @@ How to install:
         DefaultDays => 7,
     );
 
-5. patch /Ticket/Elements/ShowSummary if you are using rt < 3.9
-    $ patch /path/to/Ticket/Elements/ShowSummary < /path/to/rt/local/plugins/RT-Extension-JSGantt/etc/jsgantt-showsummary.diff
 6. restart RT
 
-
 How to update jsgantt.js and jsgantt.css:
 
 To make it work better with RT, we changed original jsgantt.js and jsgantt.css,

etc/jsgantt-showsummary.diff

-diff --git a/share/html/Ticket/Elements/ShowSummary b/share/html/Ticket/Elements/ShowSummary
-index 21c53c5..264dcdc 100755
---- a/share/html/Ticket/Elements/ShowSummary
-+++ b/share/html/Ticket/Elements/ShowSummary
-@@ -107,6 +107,7 @@
- 
- % my (@extra);
- % push @extra, titleright_raw => '<a href="'. RT->Config->Get('WebPath'). '/Ticket/Graphs/index.html?id='.$Ticket->id.'">'.loc('Graph').'</a>' unless RT->Config->Get('DisableGraphViz');
-+% $m->callback( %ARGS, CallbackName => 'LinksExtra', extra => \@extra );
-     <&| /Widgets/TitleBox, title => loc('Links'),
-         title_href => RT->Config->Get('WebPath')."/Ticket/ModifyLinks.html?id=".$Ticket->Id,
-         class => 'ticket-info-links',

html/Search/JSGantt.html

@@ -2,13 +2,7 @@
     Refresh => $session{'tickets_refresh_interval'} || RT->Config->Get('SearchResultsRefreshInterval', $session{'CurrentUser'} ),
     &>
 
-% if ( $m->comp_exists( '/Ticket/Elements/Tabs' ) ) {
-<& /Ticket/Elements/Tabs, Title => $title, Query => $ARGS{Query}, &>
-% } else {
 <& /Elements/Tabs &>
-%# this space is to make following elements a bit lower to avoid overlap
-%# &nbsp;
-% }
 
 <div style="position:relative" class="gantt" id="GanttChartDIV"></div>
 <script>