Construct Clashscore2 that uses Probe2 and Reduce2

[russell-taylor]

Make phenix.clashscore2 and mmtbx.clashscore2 that uses Probe2 and Reduce2

mmtbx/command_lineclashscore.py is a script that runs mmtbx/programs/clashcore.py.

mmtbx/programs/clashscore.py is a script that runs Reduce and Probe on input files and returns a list of clashes

• mmtbx/validation/clashscore.py has classes that it uses
• It is run as phenix.clashscore