Doxygen cleanup

[ischoegl]

Changes proposed in this pull request

This PR collects final doxygen cleanup steps in the context of Cantera/enhancements#179

• Sort BibTeX file alphabetically to reduce future merge conflicts.
• Replace remaining single-letter Doxygen commands \a, \b, \c, \e, \p by @b, @c and @e
• Fix some LaTeX issues

If applicable, fill in the issue number this pull request is fixing

Closes Cantera/enhancements#179

Checklist

• The pull request includes a clear description of this code change
• Commit messages have short titles and reference relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• Style & formatting of contributed code follows contributing guidelines
• The pull request is ready for review

[ischoegl]

@speth ... while there is clearly more potential for improvement, I am starting to see diminishing returns. Anything beyond can wait until after Cantera 3.0.

[ischoegl]

Rebased. Merge conflicts should (hopefully) wash out soon.

[ischoegl]

@speth ... resolved merge conflicts, so this is ready for a review.

[speth]

In the long run, I think I might prefer Markdown-style formatting over the Doxygen-specific @e, @c etc, but this is fine for now.