WIP on minor cleanups in main.cc of the sequencer.

* Added test builds of the sequencer to the cmake to facilitate building and debugging (non-functional as it does not build the dbd file, cmd file, ...
* Wrap the local EPICS variables in a new type to promote type safe read/write of data, plus give us a point to allow mocking the interface out.
* the casdf sequencer does not build right now.