Support Qt5

[Joern Ungermann]

Qt5 is getting more support and, supposedly, Qt5 should be very compatible with Qt4, so the effort to switch to Qt5/support both might be small. At least for my general conda installation, conda tends to upgrade to qt5 quite often forcing a manual downgrade (which of course can be remedied with a dedicated conda environment for MSS, but that is rather complicated for the average user).

[Reimar Bauer]

Made a draft of a pyqt4/pyqt5 compatible MSS version.

Resolve Issue #114.

→ <<cset c39a735daa0c>>