glvdebug: Move QReplayWorker into a separate thread.

glvdebug: Move QReplayWorker into a separate thread.

* In order to achieve this correctly, the QController could not inherit from the QReplayWorker; instead the controller now has a worker object. The QReplayWidget puts the worker on a separate thread.
* Any interaction between the QReplayWorker and the rest of the UI must be done through Qt's signals and slots, which knows how to pass data between threads.
* Performance of replaying within the UI is now on-par with replaying using glvreplay64 from the command line, based on the cube demo. Increasing the validation level will slow down the replay preformance (as expected), and printing of validation messages will also slow down replay performance (as expected).