python-uci: simplify Makefile by using sources from PyPI
As pyuci is now on PyPI, I was able to simplify Makefile It means that we will download sources from PyPI.
- In this case, we don't need to have anymore PKG_SOURCE_* variables.
- Also, we don't need to update manually PKG_MIRROR_HASH by running make package/foo/download and make package/foo/check
It would be enough to change just PKG_HASH and that's all. PKG_HASH we can get on PyPI.
While at it, I added variable PKG_LICENSE_FILES and added source package
Compile tested for Turris MOX, HBD.