Oracle fix

Since oracle has no boolean data type, I changed the mapping to a NUMBER(1). That's the fix for https://jira.duraspace.org/browse/FCREPO-1208 and everything seems to run smoothly.
The second commit is just some optimization since fetching all Tables in Oracle XE took ages for me. There is still a call to fetch all Tables in the Rebuilder, but I was reluctant to change it since I am unable to test it. maybe someone wanna tweak the call to DatabaseMetadata.getTables() as well.

Have Fun!

Frank