Issue 84 heap parsing in separate thread 1

fixes #84 

not huge improvements:

- parsing of heap dump happens in a different thread
- added helpers to convert msgpack objects into qt specific classes
- added an event parser which parses event collection
- iterating through object dump is fast, but converting objects to ObjectDetail is still slow.
  + maybe we should not convert to msgpack::object to objectDetail, and persist objects directly to db.
I was hesitant to use signals and slots here because passing the data across to `heapWorker` will involve copying the data, I think. Also I was thinking `RbkitMainWindow` class should not even care that heap snapshot is happening in another thread. Shouldn't that information completely encapsulated within Subscriber object?