Cleanup swim wrapper

[baltzell]

In preparation for new swimming versions, do a little reorganization of org.jlab.clas.swimtools:

• Move stoppers to a new, separate class Stoppers
• Move parameter setup to a new, separate class SwimPars
• Add ISwim interface of appropriate methods from Swim
• Add abstract ASwim for shared data and generic wrapping of some simple geometry calls
• Old Swim and new AdaptiveSwim classes now extend ASwim
• Move existing adaptive methods, previously unused, to AdaptiveSwim and add missing ones
• In the process, removed some unused Swim methods
• General cleanup