Refactor & new analysis functions

[txie-93]

• Refactored the code. It now only reads the trajectory once. Significantly improved speed and memory use.
• Several new analysis functions.

[danielschweigert-TRI]

LGTM!
Could you add a change related to a previous PR?
I want to make a small change to the keys in REQUIRED_METADATA:
'temperature' --> 'temperature_K' (unit Kelvin)
'timestep' --> 'time_step' (follows format of other keys, i.e. individual nouns separated by _)

I believe that also requires updating all of the meta.json files in the S3 folder. Hope this is easy to do.

[txie-93]

I like your suggestions! Yes, it is easy to do. temperature_K looks a little odd though. We don't include units for other properties. Should I just change 'timestep' --> 'time_step'? @danielschweigert-TRI

[danielschweigert-TRI]

Sounds good to me. I am just worried that there could be confusion on the temperature unit; unless it's understood that K is the standard unit used.

[txie-93]

Done! I updated both the code and the data. Merging the code now.

K is quite standard in my opinion, but this is a good point. Let's keep it as it is for now, and we can change in the future if we like.

[danielschweigert-TRI]

👍