API doc-comment cleanup.
Merged CBL_Database into CBLDatabase

*whew*!
Finished renaming CBL_Database to CBLDatabase

(Just search/replace and file renaming in this commit)
Renamed -[CBLRevision initWithCBLDB:] to -initwithDatabase:
Fix: Creating DB with invalid name fails silently

-[CBLManager createDatabaseNamed:error:] wasn't setting the error if the
call failed due to an invalid database name. (Fixes #4.)
Also added an out error parameter to databaseNamed:.
Internal cleanup of database-instantiation API.