Bundle swisseph data files into pyswisseph-data-*

[ShadowJonathan]

This is a tracker/reminder issue about bundling the swisseph data files into pyswisseph-data-* packages, to make it easier for users to access different datasets dynamically through pip itself.

[astrorigin]

Cool idea, but:

• Download and installation of data files is (and has always been) the responsability of the user or application developper.
• Debian systems have native packages just for them (swe-data).

[ShadowJonathan]

(After some discussion;)

We could still publish the data files, and when installing, give a dummy Python package (like swisseph.data, under swisseph/data/__init__.py), that in actuality only exists to locate files relative to it, so that we can package data files like that, and system-installed data packages and pip-installed data packages will resolve properly no matter their location (as long as it is in a resolvable Python import folder)