fixes for answer key, QA feature text and top page margins
clean up of mathML testing section, exercise testing and various testing fluff code
fixes for equation numbering, try-it header space, top page space reduction and misc fixes
adjustment of top and bottom page margins to accomodate custom introductions
updating figure alignment constraints for 150dpi imagery
adding economics and psychology css files
Merge branch 'master' of https://github.com/Connexions/oer.exports
fix of conflicts in history and merge with updated master
Merge pull request #373 from Connexions/precalculus-bugfixes

PreCalculus bugfixes for miscellaneous layout issues, figures, page margins and spacing