Repo Maintenance --> Setup Branch structure

[bosd]

In odoo repo's it is common to use a branch name similar to the odoo version.
E.g. 14.0, 15.0, 16.0, 17.0
For each version, we start with a fresh new branch.
Then per module a PR is created to migrate the code from the previous version to the next one.
14.0 --> 15.0
In the PR the complete commit history is preserved. And a migration commit is added on top.
eg

[add] base_monero
[MIG] base_monero: Migration to 15.0

We should follow this workflow here in this repo as well.

Tasks:

• Delete main branch
• Set 14.0 branch as the default
• Delete the "dirty" 15.0 branch
• Create new EMPTY 15.0 branch
• Create new EMPTY 16.0 branch
• Create new EMPTY 17.0 branch

@serhack @cryptochangements34 Can you take care of this?
Edit: If you give me the permissions, I'm also happy to do it.

new empty branch can be created with.

$ git checkout --orphan NEWBRANCH
$ git rm -rf .

[bosd]

cc: @tobiaskeute