Documentation clean up and update

[ChiCheng45]

Description of work
Update to the documentation.

• Remove some old rst files which were no longer used.
• Removed unused images.
• Changed Correlation Functions section to Time Series, it now includes a section on resolution function used in MDANSE.
• Added Weight Scheme section which describes how the total are summed up from the partials.
• Added q-Vector Generation section.
• Updated all analysis job sections. In particular, all equations have been rewritten so that they follow the same notation throughout. Analysis job that are no longer available or are still in development have been marked.
• Added Symbols and Notation section.
• Removed a number of How-To Guide sections.
• Removed Dynamic Coherent Structure Factor tutorial.

Feel free to make edits to this branch.

Fixes
Closes #411
Closes #375