A bunch of fixes:
- Fixes #76 : Issues when just using #include <Qtilities>
- Fixes #77 : Compiling TreeNode on MSVC gives the following warning: 'class1' : inherits 'class2::member' via dominance
- Fixes #75 : Check new QStandardPaths class usage in Qt 5 for QtilitiesApplication::applicationSessionPath()
- Fixes #70 : Update extension system to work with Qt 5
- Fixes #78 : QTILITIES_NO_HELP does not exclude dependencies on QtHelp everywhere

This commit also contains 99% of changes required to make Qtilities work with Qt 5.