Update SOCI to latest master.
SOCI boost::tuple leak test
Database access:
	created own boost::optional<> clone and boost::tuple type conversion for SOCI, to workaround bugs (or "features") and tuple memory leak (see tests/soci-tuple-leak.cpp)
	implemented prepare-once-use-many-times-with-different-args insert/update and select statements (now properly, without preparing statement per exec)
	tests for everything above.