Changed the relationship between EpiLight and Sweeper.
In particular, for triggered video acquisition, user now has to manually set up a TTL pulse to control the light.
This is perhaps slightly more arduous for the user, but eliminates the somewhat opaque coordination between EpiLight and Sweeper that never seemed entirely satisfactory.
Now at least it should be easier for the user to form a mental model of the program's operation.
Changed the name of Step Pulse to Built-In Pulse, of Syn Pulse to Built-In TTL Pulse.  Also unified that way those are calculated.  Also added a Pulse Builder and a TTL Pulse Builder.