Add database queue & doTransactionWithBlock method

The goal is to replace beginTransaction and commitTransaction with a routine including queue management.
Managing a queue avoids the risk of having two SQLite transactions getting nested, which is illegal.
Implement the use of the new transaction block routine

Replace calls to beginTransaction and commitTransaction, calls to @synchronized(db).
Slightly modify some transaction borders.
beginTransaction and commitTransaction are private from now
Serialize accesses to sqlDatabase.

The access is serialized through the combination of another queue and dispatch_sync.
Inspired by Brent Simmons’ article <http://www.objc.io/issue-4/SQLite-instead-of-core-data.html> and FMDatabaseQueue.
After fetching a feed, run callback routines asynchronously.
Code cleanup
Prevent lock when deleting folder
Minor optimizations
Restore 32bit compatibility
Systematically close FMResultsSet when they are not needed anymore
Handle file:// URLs

Fix issue #279
Fix sync issue when one deletes articles before marking them read

See <http://forums.cocoaforge.com/viewtopic.php?t=26526> and <http://forums.cocoaforge.com/viewtopic.php?t=26456>
Silence some Xcode warnings
Spanish localization sent by Juan Pablo Atienza Martinez
Update ad blocking URL lists

As suggesting at <http://forums.cocoaforge.com/viewtopic.php?t=26548&p=138316>
Update AISHTTPRequest to current pokeb/asi-http-request
Update FMDatabase to current state of ccgus/fmdb
Make clientAuthToken a GoogleReader property
Fix a memory leak on PXListView

Successive calls to -cacheCellLayout could lead to memory being allocated without being freed.
https://github.com/Perspx/PXListView/pull/30
Cosmetic changes to memory management

Note to self : many of these CFXMLTree commands are deprecated, and seem to leak.
Will need to review this later.