Add the possibility to compile Dwarf Therapist with Qt5

I added the possibility to compile the latest version of Dwarf Therapist with Qt5, for those who can. It can be useful for people who can do it and who want to use the latest version of DT.  It is always possible to stick to the Qt4 version. 

I had to change the step of compiling DT, because I didn't succeed to compile with Qt5 through the previous way; but is probably because I do not master the subtleties of qmake and make.

I hope it is quality enough to be incorporated.