support for escaping SQL special characters (UI & featurestore config to...

... activate support in GeoTools)

This is the companion request to https://github.com/geotools/geotools/pull/186 which activates the option in GeoServer.

I've added a checkbox to the "edit sql view" page to enable escaping special sql characters (quotes - and strip backslashes)

The XStreamPersister class has also been modified to serialize the new escapeSql attribute of the VirtualTable class to config files.  I've coded it not to swallow the exception and rewind the file if it parses a config file that doesn't already have the escapeSql option defined.