Deprecation warnings for .platform,.family,.sensor

Fix ncc to use either 'platform' or '.platform' (preferring the former).
Similarly for 'family' and 'sensor' files.  If a .platform (or .family
or .sensor) file is used, print a deprecation warning for the user.
Merge pull request #201 from lab11/deprecation_warnings

Deprecation warnings for .platform,.family,.sensor