Fix #106: add pco specific camera type

This adds a pco camera device applicable to all pco cameras. It fixes #106 by patching the enums. However, there are two caveats:

1. Patching makes use of `__enum_values__` which is a real deep internal detail.
2. This change has not been tested yet.

This change should be added before #105 on which the `Dimax` type can be built on.