optimize generation counters and add Directory object mutex
fix sensitive and extractable in derive*DH()
implement C_CopyObject
Merge pull request #21 from fxdupont/genopt

optimise generation counters
Allow specifying whether a transaction will be read only or read/write.
Prefer to instantiate an OSToken via factory method.
Prepare OSToken to be derived from an abstract class base.
Insert ObjectStoreToken base class that will allow the for storage backend to be switched out for another implementation.
Make object store storage backend configurable via softhsm2.conf
Initial naive implementation of object store database backend for token object storage.
Hookup backend selection "file" or "db" via softhsm2.conf: objectstore.backend = db
Make database storage backend optional via configure.
Don't compile database backend unless "configure --with-objectstore-backend-db" is used.
Fix warnings.
Lowest level test for the object store database backend.
Added tests for DBOject class.
Added tests for DBToken class.
Remove superfluous #include.
Fix spelling mistake in test name.
Database backend object store tests.