Add comments indicating default copy/assign

StFmsCluster, StFmsClusterFinder, StFmsFittedPhoton, StFmsTower,
StFmsTowerCluster

See issue #15
Remove StFmsPoint copy constructor

Use compiler-provided default. See also #15
Disallow copy/assign for some classes

Affects StFmsPointMaker, StFmsClusterFitter, StFmsEventClusterer,
StFmsGeometry

Closes #15