SP adaptSynapses: Experiment with discouraging shared inputs

[chetan51]

As per #892, might be worth experimenting with the following approach:

"Permanence values for shared inputs, which are input bits that are turned on and connected to more than one active column, are decreased in order to discourage multiple columns from learning the same input pattern."

[subutai]

For reference it was implemented in FDRCSPatial2.py as the parameter synPermActiveSharedDec. I don't know that we ever proved it was useful.

[rhyolight]

@subutai I think this should be done in the research repo. I'm not sure it should be reported here.

[subutai]

Moved to research repo: numenta/nupic.research#576