* removed delete call
* cleanup
* lower cpu activity of log thread too
* fix log messages
* do not enter threads into unordered_set, as it is unneeded
* do not compile in calls to disabled plan cache
* moved AQL regex cache from thread local variables to a class of its own
* more sensible thread creation and destruction
* simplify index API a bit
* fix fulltext index removal performance, simplified code
* updated CHANGELOG
* fix hanging test
* try to fix shutdown problem
* improve fulltext query performance
* fixed duplicate var
* removed obsolete code
* fix some shutdown races
* do not call ensureIndex that often