Get rid of support needed by Direct for generated classes via a context class loader.
Can then have just one script manager, with an ordinary class loader, and no context class loader switching.
merge MMcM: Get rid of support needed by Direct for generated classes

Merge pull request #1523 from MMcM/sql-layer/remove-direct-classloading
https://github.com/FoundationDB/sql-layer/pull/1523