Coordinate multiple prop types with config file args overriding command-line args

[bestchai]

Now that multiple prop types can be input, it's possible that someone inputting a config file and expecting the prop type in the config file to override the command line one may instead mine two prop types. Investigate + fix.

[Issue created by carolemieux: 2015-10-04]
[Last updated on bitbucket: 2015-10-05]

[Comment created by bestchai: 2015-10-05]
I think that the default arg behavior for prop types is to have them be cumulative -- each -f arg adds a new type to mine.

However, in the case that the user may want to override types specified on the command line so far, we can add a new binary arg that changes this default behavior to mine just one prop type -- the last one specified on the command line.

Another issue with cumulative/multi prop type mining are the global semantics of support/confidence thresholds. At the moment there is no way to specify these thresholds per property type.. perhaps a new issue should be created for supporting custom thresholds per prop type.