Support for energy per mole in H5MD

[JFRudzinski]

Added support for use of energy/mole e.g., KJ/mole as units for energy quantities

[JFRudzinski]

@Bernadette-Mohr I just made some small changes to support usage of energy per mole quantities with the H5MD parser. Take a look and let me know if you have any suggestions or questions.

Also, I thought this would be a good opportunity to walk you through rebasing just to make sure we are on the same page, since it is our standard way for updating changes that have been made to develop after we have already checkout out a branch.

So, go ahead and create your branch for the small adjustment to the Gromacs parser, and then let me know when you have done that. I will then merge this branch (after your review), and then we can meet to do the rebase, ok?

[coveralls]

Pull Request Test Coverage Report for Build 9583990891

Details

• 5 of 7 (71.43%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.02%) to 88.146%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
atomisticparsers/h5md/parser.py	5	7	71.43%

Totals
Change from base Build 9112725076:	-0.02%
Covered Lines:	6239
Relevant Lines:	7078

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💛 - Coveralls

[Bernadette-Mohr]

I guess the amount of substance will most likely be given in mole, we probably don't need to cover any more esoteric options. I don't see any issues.