This is a pure extension and fully backwards compatible.
* Adds support for running it as a pre-compiled library while still being able to
choose my `QXxxApplication` class at build time.
* Be able to decide at runtime whether to use the single
instance stuff (without starting a server and so on).
* Add CMake support
* Remove unused 'tr()'
* Add option to specify a class for inheritance
* Use modern syntax
* Rework CMakeLists.txt
Thanks to @akallabeth
* Add CMake build rules for examples