PhysConf: add new module to make imports for "Selection" framework a bit more more intuitive
- add module python/PhysConf/Selections.py
It allows to provide "Selection" framework with a bit more intuitive syntax: now one needs to import selection objects from PhysConf.Selections instead of a bit cryptic PhysSelPython.Wrappers
from PhysCondg.Selections import SimpleSelection, SelectionSequence ## new
from PhysSelPython.Wrappers import SimpleSelection, SelectionSequence ## old