Reorganization of diarc

The organization method used for v0.0.1 showed several shortcomings, in particular that things like qt_view could not see topology because it was in a higher level directory. This only worked in run.py because topology was in the same directory as the executing code. 

This places all the core diarc code in a diarc subpackage. The root directory can also be treated as a python directory, with an __init__.py that adds the contents of the diarc subpackage to its own search path. This allows the root directory to be used as a python package in the same way as the internal diarc package.