Add support for defining the Run target and the arguments within a qmake project file

This task is about adding support for defining the executable and it's arguments for the "Run Configuration" of QtCreator within a qmake project.

This is useful when projects have a QML only and don't provide a executable by it's own. In this case, it should be possible to define what executable QtCreator should use to run this UI and also the arguments needed for it.

One way of doing it, would be to parse for two new qmake varibles:
QTC_RUN_EXECUTABLE
QTC_RUN_ARGUMENTS

Although qmlproject can be used for QML-only Uis, this doesn't work for bigger projects, where plugins need to be build in addition to the QML UI. E.g. the examples of qtapplicationmanager, which are QML-only, but need to be run using the appman executable and some additional arguments.