[FEAT] Calculate the ion temperature

[aaronjridley]

Is your feature request related to a problem? Please describe.
The bulk ion temperature needs to be calculated

Describe the solution you'd like
Once the collisional heating terms are in place, it should be trivial to calculate the ion temperature, since it is mostly a balance between the different collisional heating terms.

Describe alternatives you've considered
The real question is whether to implement a parallel and perpendicular temperature for the ions. Not sure. Need to look at the equations to see how complex they are. This could be put off for a bit.

Additional context
Lindsey whats-her-name from Canada does the parallel and perp temperatures. I need to find her paper.

[Ionospheres]

GEMINI-TIA does parallel and perp temperatures (doi: https://doi.org/10.1002/2016JA023329). It isn't too much more complicated than just having a bulk temperature. There is the computational resource cost of solving another equation so having a flag for this option could be a good thing depending on the user's needs/modeling scenario.