Add generic python recipes

[Begasus]

I've been using this generic recipe for a while now, could be handy for others too?

[waddlesplash]

IMHO, we should do something about the "duplication" of all this logic in every Python recipe.

Perhaps we should have a "templates" directory in the HaikuPorts repository with scriptlets/functions for specific recipe types, which could then be invoked and take care of the general logic here?

CC @korli, @OscarL

[OscarL]

After reading haikuports/haikuports#2541... maybe something like korli suggested in his comment there?

Edit: we might need a couple of variants of that, as older packages tend to use "python setup.py build install" (via setuptools), and most newer ones do not have a setup.py anymore, using "pyproject.toml" (PEP-517) instead (thus requiring using "build" and "installer" on them).

Still, sounds like something worth doing. Perhaps after we finish cleaning up the 2.7/3.7 versions?

[Begasus]

Made some changes to the default python recipe and added one for those using whl archives and one for using build/installer in the source.
For me they are a nice thing to have around to create a recipe for python packages quickly.

[OscarL]

Some minor nit-picks regarding spacing, and some suggestions removing unneeded variables and dependencies.

The --skip-dependency-check is there because the dependencies it list are, AFAIK, runtime dependencies. If some of those are also build-dependencies, I prefer to to let the build fail and add them manually as needed.