Merge pull request #2781 from tufanbarisyildirim/develop

EXISTS / NOT EXISTS clause support for  DB_driver
Polishing changes from #PR #2781

Looks like an unnecessary commit was made by the author just as I was clicking the Merge button. :)
Remove unneeded manual escaping of session data
Remove _serialize() and _unserialize() methods

Since removing the unneeded manual escaping code, there is no-longer any reason
to have the serialization functions abstracted. This also allows us to only
suppress errors when unserializing cookie data, and only trim when we are
unserializing database data (see commit 6b8312).
Merge pull request #2784 from captbaritone/bug/unneeded_session_code

Remove unneeded manual escaping of session data
Update Forum and Wiki links in Readme

Old links were 404ing
Merge pull request #2790 from captbaritone/patch-2

Update Forum and Wiki links in Readme