ini style config files

Addresses #363 and #369.

This implements ini style config files using the standard Python ``ConfigParser`` module.

Most options go in the ``[tangelo]`` section, while girder options go in ``[girder]`` and VTKWeb options in ``[vtkweb]``.

I decided to simplify things a bit - if a config file is not specified on the command line with ``-c``, then the defaults will be loaded; there is no more sequence of search locations.  Such searching can be deferred to startup scripts on a per-deployment basis.  As we approach 1.0, I'd like to keep things as simple as possible to aid in testing and debugging, etc.