Add support for workflow that leverages interactive development using cling in QtCreator

cling is the evil step-sister of clang (LLVM C++ compiler). It was made by CERN to shorten their development cycle by allowing some code to run interpreted so you can quickly test before comitting to a full re-compile.

Link to cling: https://root.cern.ch/cling

I think that there is a clear business case for supporting this workflow from within QtCreator. It would be a killer feature that would set QtCreator apart from all the competition. Imagine opening one of the examples and pressing the "pre-play" button and instantly seeing the example in action without any compilation. Also you would be able to change the code while the program was running and see the changes instantly.

A monitor window would show you the internal status of cling with useful debugging details and an interactive commandline where you could type one-off commands (much like the python interpreter).

cling has been successfully been used with Qt as clearly shown in this video: https://www.youtube.com/watch?v=BrjV1ZgYbbA