Fix crash in Collection::postRun

- replace lock()/unlock() pairs with QMutexLocker - for exception safety
- lock also m_runningChildren, since slocChildrenStopped() is probably
  called from UI thread, and all other accesses are from timer thread.
More mutex fixes - master timer

- use QMutexLocker
- add/fix comments
Merge branch 'master' of https://github.com/mcallegari/qlcplus
Even more locking improvements

- MasterTimer::m_startQueue is not locked properly in tickTimerFunctions()
- replace lock()/unlock() with QMutexLocker() where possible (I skipped cycles with temporal unlocking)
- fix comments (that were copied from another place and were not updated)
Merge pull request #180 from janosvitok/master

Fix for Collection crash + some mutex fixes