DAR-729: Make the edit page layout and preview responsive

Parent ticket: https://wikia-inc.atlassian.net/browse/DAR-729

This changeset introduces style and script changes to make the edit page work with the responsive layout.

### Responsive Edit Page
https://wikia-inc.atlassian.net/browse/DAR-887

- Cleaning up edit page layout templates and styles
- Overwriting styles to make the edit page responsive
- Fixes for wide mode (main pages and normal article pages)
- Fixes for autoresizing (these apply regardless of the responsive layout)
- Adjusted font sizes inside the editor to their new sizes when responsive layout is enabled

### Responsive Edit Preview
https://wikia-inc.atlassian.net/browse/DAR-886

- Fixed preview content area size for responsive layouts, with the exception of some edge case screen sizes in Webkit browsers (see comments in diff for more details) -- the PO has signed off on this solution.
- Fixed some margins and paddings that weren't accurate anymore (probably since the grid update)