Conversion of plotUtils to use coordConv (from utils/coordUtils)

This removes a great deal of code from the \__call__ of class mapObj and uses a separate module (that is, coordUtils) instead, making mapObj more streamlined and making coordinate conversions available for other code to call without the need to create a mapObj each time.  (Previously that was necessary even if no plotting was being done.)  This is the reasoning behind the creation of coordUtils (#50) and now is implemented in plotUtils.  Other module conversions to follow.