[Qt-creator] Plugin to display compile errors warnings etc. inline

[Daniel Teske]

After reviewing our code in BuildManager and TaskWindow, I did the refactoring 
that was overdue of getting the actual task distribution out of the 
BuildManager and made the TaskWindow a internal class. 

I introduced a *TaskHub* which essentially emits all the task related signals 
the buildmanager had, and also the new signals you need. 

daniel