Draft: Add project specific gitconfig and more

This is a pull and modification of changes introduced to turris/turris-os-packages@848af2d4

It introduces primarily project specific config that includes new scripts and hooks. To enable it in local repository it is just:

git config --local include.path ../.gitconfig

The hook checks if commit being pushed to Gitlab server is correct. There are multiple checks:

• Check naming convention
• Check base (hbk vs hbl vs hbd)
• Protects against forgotten hbl and hbd pushes when pushing hbk or hbl

In terms of aliases this adds:

• git new-mr

  This opens web browser with new merge request on https://gitlab.nic.cz for current branch.

• git new-branch

  This creates new branch interactively and should help users with naming convention.

This adds same functionality as there is now for turris-os-packages thanks to turris/turris-os-packages!574.