Standardized commenting in custom.css file

Standardized commenting blocks, plus better spaced out css declarations
for easier reading by users.
Converted tabs to spaces

Converted tabs to spaces so everything lines up properly.
Updated external resource versions

Updated BootStrap to version 3.2.0, updated FontAwesome to version
4.2.0, added FontAwesome to editor.css, changed Bootswatch theme to
Flatly.
Fixed errors in form validation rules

This file needs to be modified according to what forms are used on your
website.
Added commenting to validation rules