Arkane's output.py file should be restructured

[alongd]

We all agree that the Arkane output.py file should be restructured. One possibility for a format change, as suggested by @amarkpayne, could be outputting a nice HTML instead.

We plan to output RMG libraries in Arkane (thermo + kinetics), which makes the thermo and kinetics blocks outputted to this file unnecessary, and also confusing.

Also, the current conformer block is generated using Abstract Syntax Trees, which is hard to maintain, perhaps we could replace it with a simpler code.

[JacksonBurns]

We had been talking at dev hours about also potentially reworking the input file to accept a markup language rather than python-formatted file - thoughts on combining these ideas?