Remove code from repo and small CI improvements

Code shouldn't be in the pmaports tree, so let's remove it. I made separate repos for every application we use that has the code in our tree, and moved the source to it including it's git history. Finally we have proper package versions and per application CI, issues, merge requests, etc.

This also means the flake8 check now only checks testcases in .gitlab-ci/testcases. While I modified that, I took the opportunity to split the testcase linting out from the shellcheck. The Clang C linting test is now also removed, as it's in the application repositories instead.

Except for the wiki check if a device port is made, the first stage of the CI is now allowed to fail to allow people to see if their package actually compiles before they start fixing linting issues. Of course an MR should still never be merged when it's marked with an exclamation mark, except for cases like this MR where the $pkgver switches to a new versioning scheme as defined by upstream sources.