- Upgraded doxyfile to latest format
- Fixed a bunch of warnings and errors in docstrings that doxygen was complaining about
- Added the doxygen-awesome theme to modernize the output
- Removed a duplicate screenshot we'd had in the docs folder
- Moved the RecastDemo screenshot into the Docs/images folder
- Changed the doxygen main page to be the README.md since the dedicated main page file we had was nearly identical but out of date
- Added CONTRIBUTING.md so it's part of the generated doxygen output
- Removed duplicate license file to avoid confusion
- Combined the FAQ with the Recast_api.txt, since the FAQ was essentially just better docs for the members of `rcConfig`
