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

Assorted bugfixes for PreCalculus text involving fixes for figure alignment, top page spacing reduction, misc layout fixes, try-it feature body paragraph broom up, answer key layout fixes, fix to Key Terms header, and other fixes.

This changeset includes fixes for the following github issues: 
#199, #200, #201, #202, #207, #208, #211, #213, #215, #242, #363