Pymap3d

Full functionality of PyMap3D (as with Python in general in 2019) requires Python ≥ 3.5, but a useful subset is made available to Python 2.6, 2.7 and 3.4. This is relevant to MicroPython and ROS users and other special use cases where currently supported Python versions may not yet be readily available.

Put Ellipsoid() in its own file for clarity and flexibility with other packages.

ECI functions previously had an API unlike other PyMap3D functions, they are now the same as the rest of PyMap3D (scalar or N-D array for each variable).

added several tests so that Pandas and Xarray are functioning.

Also handles ecef2geodetic scalar input.

AER2GEODETIC was always going to the default WGS84 ellipsoid since the `ell=` argument was not present. We have fixed this error.

Also did a complete rewrite of documentation to `numpydoc` standards (mostly) and regenerated with pdoc3.

Corrected algorithmic error for `ecef2geodetic` where negative altitude wrapped to positive altitude

parameterized tests to provide better coverage of singularities / edge cases

use pdoc instead of sphinx for autogen docs

Don't limit altitude to be positive in `geodetic2ecef`, useful for near-earth WGS84 not exactly matching Earth's complicated surface.

Improving accuracy and computation speed, a more modern closed form ecef2geodetic is implemented.

More self-tests.