Bubble ex gdml file additions

BubbleEx simulation now reads gdml with most geometry in gdml files. still need to create sweep magnet, electron dump, and adjust some of the others to correct dimensions. Once sweep magnet is created add in the magnetic field at detector by changing the existing but commented out code at the bottom of the detector class file to point to correct naming convention. can also re add the command abilities which were originally commented out, by reinserting with correct pointers and defining the pointers in the detector messenger class.