fixed some errors in shell points. also fixed it so the shell and trajectory geometries get their extra variables.

Formatting and dummy code for geometry functions. For trajectory/tecplot format we should do things a little different.

Tecplot documentation update

See merge request swmf_software/swmfpy!5

Made tecplottools.apply_equations more robust, anticipated some different formats in equations files

- Google style docstrings use `Args:` and not `Arguments:`
- Stick to markdown *everywhere*.
- The first line in a big docstring `"""` is always a one line summary

Please confirm before I merge :).

Version 2020.4 with bug fixes to retrieve time better from omni and also works with `share/Python/Scripts/prepare_geospace.py`