Updated storage of timeout variables to allow multiple users on a site to run scanner at the same time

starbow, but greatly extended by aasarava and jpsalter.

New features include ability to undo changes, to limit searches to node type and even
nodes with certain terms, to match whole words, and to designate words that come before
or after search terms, among several other changes.  See README.txt for full list of
features.

Only modifiying most recent revision in node_revisions table.
Added title search/replace.
Added case insensitive searching.
Got custom fields working.