docs(Guide): Content edits in the Angular 2 Guide. (#3159)

* Content edits in the Angular 2 "Forms" page.

* Updates based on @juleskremer's feedback.

* Added bold formatting for UI button names.

* [WIP] Copyedits to the Glossary. Includes several questions and comments--search for "CF:"

* Updated with Jules's feedback and fixed a few issues that I didn't catch the first time.

Author: cfranger