Add Bioexcel cv19 database

[jamesmkrieger]

We now have functions to fetch, convert (using mdtraj) and parse files from the BioExcel-CV19 simulation database.

[jamesmkrieger]

This needs tests too. We're also missing tests for parsePSF and writePSF that should be added too

[jamesmkrieger]

We now have tests for helper functions, structure functions and topology functions. We still need them for trajectory ones.

For convert xtc to dcd, we will also need a data file. It may also be good to move this more general function somewhere else, but probably it's fine.

[jamesmkrieger]

Try conda-forge mdtraj and find stringio fix

[jamesmkrieger]

Try conda-forge mdtraj and find stringio fix

conda-forge mdtraj was tried before. Python 2 just can't support either version.

[jamesmkrieger]

And there are still more places to check for seed alignment not full too

[jamesmkrieger]

Try conda-forge mdtraj and find stringio fix

not sure what happened with the stringio thing but it seems ok again