Add configurable custom named toolboxes

[Rickasaurus]

From #3

The idea is you add a name, path pair which represents a custom toolbox. The type provider will:

1. Make sure that it's in the matlab path at type provider and execution time.
2. Add a properly named toolbox type for the toolbox and lazily fill it with functions from the given path.

Questions:

• Should this be a lookup by name on every execution, or be compiled in?

Seems like it should be a lookup, but that means the configuration file is required for the app. Perhaps static if it can't find the config file would be ideal.