Migrate the codebase from Gatekeeper repository #516

[abstractj]

In the past month, we discussed the idea of having a new home for Gatekeeper, based on that we decided to create a new organization on GitHub and rename the project to Louketo Proxy.

This pull request refactors the codebase to the new name and should be merged only after the transfer of the repository.

Some considerations

• The documentation will be improved, but it's out of the scope for this pull-request
• Migration of the Dockerfile after the transition, that also covers #541.
• There's a lot of work to do this week, so please be patient :)

[abstractj]

@stianst thanks for reviewing. Ready for another round.