HSEARCH-1755 Making sure that DefaultStringBridge has a public no-arg co...

...nstructor

Also allowing the use of @Factory within a FieldBridge. This opens the possibltiy to re-use singleton instances,
even if @FieldBridge is used to specify bridge class.

Renaming some of the methods in BridgeFactory.
Should other implementations get a similar treatment? (I guess that would be pointless?)