make engine access happen via the implemented services instead of a large facade
make ErlangXref a normal class (not static)
use ErlangEngine as a hub for retrieving all services
fix inconsistencies with ErlangEngine
code cleanup
move getStateDir from Modelcore to ErlangEngine
make ErlideOpen available through OpenService
make sure engine is only created once
move ErlideDoc to OtpDocService
merge engine work