JPA Cache Store fails on Oracle, Postgres and MsSQL

Current snapshot version of JPA Cache Store fails on Oracle (see failed tests with stack traces), Postgres (failed tests) and MsSQL (failed tests).

While in case of Oracle and Postgres the problem is probably in __ispn_metadata__ table, in case of MsSQL problem is in "User" entity, as User is reserved name in MsSQL. Oracle has a problem with table starting with underscrore, in case of Postgres VARBINARY type used in __ispn_metadata__ is not available in. In case of MsSQL I'm not completely sure if it's bug or if it should be handled by user.