Converted BFieldSim to Python

still untested
tweaked bfieldsim

still doesn't work
Started Trap class

and filled out 'simulate' routine
Started Slower Class
Started Imaging Beam class
Fleshed out atomlightint

also broke out AtomImage and ImagingSystem
Broke out more classes
Fleshed out image operations
Got it to do trivial output!
Got linear density to pass
Fixed atomlightint
Corrected error and absorption methods

changed from analog to digital images
added dark current