Completed the first round of the abstract interface, leaving Bindings incomplete for now.  Stuff like iterators, where it makes sense, needs to be done, and documentation can be lot better.  Changed back to -std=c++11.  Moved Loc out of the core and from the term namespace, and cleaned up some code.
Fixed some problems in the ElisionException class and renamed the "core" folder to "term" to be consistent with the namespace.