Expressions - Refactor

- The A3::Arg object is very similar to the E9::Term object, so the two are
  being merged.  First step is to separate A3::Arg into it's own space, then
  add a _type member.
- Added more valid stop characters as terminators for various arg types.
- Removed redundant E9 special handling for dates, which is already built in
  to the Date object.

src/CMakeLists.txt

@@ -7,6 +7,7 @@ include_directories (${CMAKE_SOURCE_DIR}
 
 set (task_SRCS A3.cpp A3.h
                API.cpp API.h
+               Arg.cpp Arg.h
                Att.cpp Att.h
                Color.cpp Color.h
                Config.cpp Config.h