Hybrid projects

# Including CSS best practices for Hybrid App projects

Status: **Up For Review**

Reviewers: @kpeatt @rosshojo @jeffkamo @mobifydave @jansepar 
JIRA: https://mobify.atlassian.net/browse/GOLD-1164

## Changes
- Initialized new page in the css code styles and filled in what we currently have established as best practices.
@ry5n I agree with the naming convention change - that makes sense for sure.

@shawn, one of the big reason we went this way with a separate stylesheet for OS was for the sake of performance. We can keep the android styles out of the regular stylesheet served to websites, keeping the file size down to a minimum, while also minimizing the stylesheets served to native webviews. And @ry5n, Im not sure what we're selling is necessarily 'consistency' among platforms, more so the ability to manage all experiences from one place. I think having very similar experiences across platforms isn't something we should be shooting for. Having separate style sheets for each OS would give us the flexibility to be as OS-specific in our interface design as we want.