Refactor css styling to include dev-interface and user-interface

[Bill-Kunj]

Currently, src/rgov-development.css is the entire styling for all RGOV web pages. This was fine when there was only one RGOV web page, but there is an effort to put together a non-dev interface.
That effort to create a RGOV user interface separate from the RGOV developer interface makes the maintenance of this single file difficult.
The CSS for dev interface should contain dev-specific styles, and the CSS for user interface should contain user-specific styles, with shared styling refactored appropriately.