Moved inventors xpath logic repeated in apps and grants into a singular ...

...method.  Changed filename selection behavior to ignore file extension.  This is because ```processFile.rb extract report ipa123456.xml``` is a perfectly valid operation which was previously not allowed due to the user's addition of the .xml extension, as the selection regex only allowed for a .zip extension or none at all.  Added a warning that file extensions are ignored when one is detected in the filename selection.  Cleaned up spacing for equals signs in the ArgumentsParser class.

Note that due to extremely low download speed, I could only test the xpath logic with one app file from 2012 because that's all I had downloaded.  However, all I did was copy and paste the logic, so it should work fine.