Bugfix: Crash in "For" loops

• For loops could crash writing to write final_structure.mmcif before the directory had been made.

Improved consistency of printing loop information

Merge pull request #22 from molssi-seamm/dev

Improved consistency of printing loop information

Better support for rerunning/restarting jobs

• Remove 'iteration.out' if it already exists.

Starting to add loops over structures in the database

• Reorganized the documentation and changed to the standard MolSSI theme

Improved error handling

Wrote the traceback for any errors caught to item_nnn/stderr.out to aid debugging.

Cleaned up the printing.

Fixed missing printing and some small bugs introduced recently.

Catching errors inside loops

The version has two major enhancements:

1. Errors in the body of the loop are caught and can be ignored or handled in different ways at the direction of the user.
2. When looping over rows in a table, a query can be used to select the rows to operate on.

Updated for Python 3.8 and 3.9.

2021.10.13

Moving up to Python 3.8 and 3.9

Update for internal change in argument parsing.

2021.6.3

Updated for the seamm argument parser moving to seamm_util.

Added to the documentation.

Streamlined the documentation, adding a description for the plug-in.
Also tidied up the description for PyPI, which is used by the new installer, and added keywords to help with searches.