Refactoring / cleanup : getting rid of sofa2jcasMap

[Marshall Schor]

CASImpl has a hashmap sofa2jcasMap.  I think it is superfluous.  It is 
used in the method

getJCas(SofaFS).
But I think that method can be replaced with a new definition that
doesn't use this map:

getView(SofaFS).getJCas();

Is there a reason we want to have this other hash map?

-Marshall