Some time in the past, the simple fixed momentum setting for particle gun was lost.

Now we set a fixed energy if the Energy property is set, otherwise we
use momentumMin and momentumMax to chose a momentum from a range.
Also changed some printouts to show the range we chose and the final
value used during simulation.

Fix hundreds of std=c++11 compiler warningsAllow to change compiler settings in cmake/DD4hep.cmake valid for all packages.Watch out for CMAKE_CXX_FLAGS in cmake/DD4hep.cmake.Move to use Boost spirit::phoenix version 3. ---- Prepare for ROOT 6

No code changes. Common code formatting removing tabs, replacing with spaces (tab-size=-2) + emacs reformatting.