Support the JDBC DatabaseMetaData#getClientInfoProperties() method, in the sense of returning an empty result, in order to make Websphere happy.

MVStore changes: abstract storage to support off-heap storage; rename getSize to sizeAsLong; avoid importing java.beans package to speed up starting the JVM

To compile user defined functions, the javax.tools.JavaCompiler is now used if available, and no temporary files are created.

inline the "create temporary LOBs" methods into the constructor so that I can make more fields final

re-organise LobStorageBackend code a little, so we don't need to correct the precision of a CLOB later on

Simplify the code and only store DataHandler.