added Aperture lens type
Big commit here. 1) added option to turn off B or E fields entirely. Need to add ability to do individual field compononets. 2) set the permitivity and permiability to vacuum levels in field calcultations. dielectric constants only effect the frequency, not the field. 3) added a method to calculate the neccesary phase shift for a TM010 cavity such that the vz in and vz out are equal.
added some new options
minor changes, not important