Andor adapter: changed the way the driverguard is used in the snapImage function.  Also treat external trigger more like software and internal trigger to make dual camera acquisitions work.
Andor adapter: changed the way the driverguard is used in the snapImage function.  Also treat external trigger more like software and internal trigger to make dual camera acquisitions work.

git-svn-id: 03a8048b5ee8463be5048a3801110fb50f378627@7903 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd

kmdouglass/Micro-Manager,kmdouglass/Micro-Manager