Pyvalem

Better LaTeX output from isotopes and states.

* Forbid whitespace within key-value pairs
* Allow whitespace, semicolon or commas to delimit states in StatefulSpecies

* Omit superscript "1" from singly-occupied AtomicOrbitals in AtomicConfiguration
* Omit semicolon delimiter in HTML output of StatefulSpecies states

- Allows `"e"` instead of `"e-"` as a valid electron formula string.

- Add GAMMA as a valid MolecularTermSymbol Lambda value
- import State ABC and all the states exceptions into the states namespace