Macro API Additions

To address issue #22, this is a possible addition to the macro API to make filtering tokens easier and allow checking of GM status.

Implements: 
boolean player.isGM() to return if the current player executing a macro is a GM or not
List MapView.getSelectedOwnedTokens() to return a list of tokens that the current player both has Selected and Owns.

Mostly for the sake of convenience and clarity.