pyproj 3.0.0 release ideas

[snowman2]

I am thinking about doing a breaking release for pyproj that better supports the new features in PROJ 7.0 (#574 ). It will probably be a while before it happens as I would like to get a 2.5.0 release and some bugfix releases afterwards first. But, I want to get this out in the open to hear some thoughts and ideas. I plan to open individual issues for each of the bullet points below.

New Featues

• Better support for PROJ RFC 4 (https://proj.org/community/rfc/rfc-4.html) through c-api (ENH: Replicate projsync for pyproj #572)
• ENH: Use 'proj_get_units_from_database' in the get_units_map() function. (ENH: Use 'proj_get_units_from_database' in the get_units_map() function. #619)
• ENH: Add support for radians for Proj & Transformer.from_pipeline enhancement (ENH: Add support for radians for Proj & Transformer.from_pipeline #612)
• ENH: Add network methods to Transformer (ENH: Add network methods to Transformer #629)

Features to drop:

• PROJ datumgrids in wheels because not needed with RFC 4 (DOC: Add transformation grid documentation page #628)
• Deprecate pyproj.transform & pyproj.itransform (Deprecate pyproj.transform & pyproj.itransform #532)
• Support for PROJ < 7.2 (better enables support for new features & future compatibility) (PROJ 7.1.0 #599 & Minimum PROJ version for pyproj 3 is now 7.2 #689)
• Python 3.5 support (Drop Python 3.5 support #499)