Expressions reboot

- Created A3.{h,cpp} which will be a simpler, lightweight version of
  Arguments.{h,cpp} that does less, but does it better.
- Created E9.{h,cpp} which will be a better implementation of
  Expression.{h,cpp} that does less, but does it better.
- Integrated A3 into Context::initialize, and Arguments and A3 will
  coexist until A3 surpasses Arguments.

src/CMakeLists.txt

@@ -5,7 +5,8 @@ include_directories (${CMAKE_SOURCE_DIR}
                      ${CMAKE_SOURCE_DIR}/src/columns
                      ${TASK_INCLUDE_DIRS})
 
-set (task_SRCS API.cpp API.h
+set (task_SRCS A3.cpp A3.h
+               API.cpp API.h
                Arguments.cpp Arguments.h
                Att.cpp Att.h
                Color.cpp Color.h
@@ -15,6 +16,7 @@ set (task_SRCS API.cpp API.h
                Date.cpp Date.h
                Directory.cpp Directory.h
                Duration.cpp Duration.h
+               E9.cpp E9.h
                Expression.cpp Expression.h
                File.cpp File.h
                Hooks.cpp Hooks.h