Doc updates

Not ready to be merged yet, but opened for comments.

The main changes are as follows:
- Slightly changed the cover page and intro to reflect the changes made this month
- Split the background into several .txt files to facilitate faster editing
- Reordered and added detail to the EoS background
- Added background to solid solution processing
- Added autoclass and autofunction calls for the new thermodynamics functions
- Added many thermodynamics references to ref.bib
Is this formula correct?