Qt Updates, master branch (2017.06.15.)

This is in order to provide proper externals for VP1 to build against Qt5.

The update fixes FindQt5.cmake and (indirectly) FindCoin3D.cmake, to:

• Set up a functional runtime environment;
• Find the externals correctly for the build;
• Set up functional RPM dependencies.

The update includes @rbianchi's development from https://gitlab.cern.ch/rbianchi/atlasexternals/tree/master-soqt-qt5LCG/External/SoQt, in a slightly updated manner. (It seemed easier to lug these updates together into a single MR.) The SoQt package was also added to AthenaExternals.

Finally, I removed APE from AthenaExternals for now, since we don't use it in master's Athena anyway. I'll re-enable it once I find the time to update the package to build APE from its Git repository.

Just pinging @emoyse on this MR as well.