simplified ErlangEngine
rename ErlServiceFactory to IErlangEngine + extension point
rename ErlangEngineImpl to DefaultErlangEngine
cleanup extra references to ErlideDoc
move ErlideIndent to IndentService
move ErlideContextAssist to ContextAssistService
move ErlideScanner to ScannerService
move ErlideSearchServer to SearchServerService
move SourcePathUtils to api
move ModelInternalUtils to ModelUtilService
make CleanupProvider an engine service
fix warning
merge engine services updates