Fix missing QTWEBKIT_VERSION_STR on Mac

Include QtWbKit header in peb.h, fixes the problem with missing
QTWEBKIT_VERSION_STR constant and makes possible to be build on Mac.
Merge pull request #1 from valchonedelchev/feature/build-on-mac

Fix missing QTWEBKIT_VERSION_STR on Mac
Introduce dark and sand themes

Themes infrastructure suggestion.
Merge pull request #2 from valchonedelchev/feature/themes

Introduce dark and sand themes
fixing faulty interaction with the Perl debugger when started from command line