Apply MSVTK style to QVTKButtons classes

[finetjul]

A coding style has been defined for MSVTK, we should try to respect the syle as much as possible: http://www.msvtk.org/content/programming-style The coding style is not perfect and probably lack some rules. Feel free to discuss rules.

This non exhaustive list of files doesn't respect the MSVTK style guide: msvQVTKButtonsAction.h/cxx msvQVTKButtons.h/cxx msvQVTKButtonsAction.h/cxx msvQVTKButtonsGroup.h/cxx

Here are some of the style issues:

• Wrong header/copyright: http://www.msvtk.org/content/copyright
• Trailing whitespaces, it shouldn't be possible to commit with trailing whitespaces, one must setup git hooks before comitting (see http://www.msvtk.org/content/how-contribute
• Don't include files in .h if not needed (see 2.B.a and 2.B.b in http://www.msvtk.org/content/code-layout-and-indentation)
• 2 space for indentation, not 4 ( see 1.D in http://www.msvtk.org/content/code-layout-and-indentation)
• Use Pimpl to hide implementation details (see 7) in http://www.msvtk.org/content/system-overview-philosophy