Total Charge / Spin Multiplicity

[ghutchis]

File import / export and input generators need better support for total charge / spin multiplicity.

If I read in a calculation, the program should know throughout that the total charge / spin is set (e.g., H3O+ or OH-, etc.)

PR #1058 gets things started

• quantumio readers need update
• input generator scripts should get total charge and spin through JSON

[matterhorn103]

We will also need a way for the user to actually set the total charge/spin for a molecule somewhere in the GUI, outside of an input generator script.

Just mentioning it here so that we don't forget :)