Added a .gitignore file - excludes backup files, compiled bytecode and egg info directories from the repository
Turning adminapi into an installable Python package:

- using src/adminapi/apps as the package root for now, since the
  adminapi app lives there inside the example project.

- commenting out the example UserAdmin - the models and the admin
  definitions should probably be moved up into the example project

- using relative imports so adminapi should work both when installed
  as a Python package and as part of the example project

- adding a setup.py file (based on the one from django-remote-forms)
Omit callable admin fields, since we don't support them yet.