numericalboxes branch ready for testing

[Laurent Valentin Jospin]

If you have time you can take a look at this branch:

https://phabricator.kde.org/diffusion/KRITA/browse/numericalboxes/

It is ready for wider testing. If all goes well we should have this in 
the next version...


Changes are (+/-) :

- Spinboxes and derived classes (SliderSpinBoxes, MatrixModels and 
UnitSpinBoxes) now can perform basic math operations on the fly.

- They become red if the expression entered is false. If there's enough 
place it also display a warning icon. (SlidersSpinBoxes and karbonplugin 
matrix model have a different behavior, they return to the last valid 
value entered but don't become red).

- All parts of krita except the old text-engine (it should be replaced 
anyway) should now use those math parsing spinboxes.

- Unitests control the behavior of those spinboxes and of the numeric 
parser they use.


If you see problems or you have suggestions feel to send it to me.


Thank you

Laurent