Adding Themes Per Session

[HopperMCS]

In regards to #7:

• Add a "gear" icon to the top-right where the "refresh" and "logout" icons are
  Done.
• Make the "gear" open a dialog with title "Customize Appearance"
  Done.
• Have a toggle for MDC Dark Theme
  MDC Dark Theme + Toggle Roadblock #30 takes this place. Don't let it hold the whole damn thing up, it's enough trouble to have its own issue.
• Add predefined themes. We can get creative with these because of the even less centralized nature of MDC. Now we can customize individual components!
  We used MDL's predefined colors.
• Allow the user to select their own colors. Add options for components, text, what have you. It's on an "as thought of" basis, really.
  Custom colors would fuck up the MD standards.
• Allow saving with user accounts
  Will obviously do.
• When logged in, theme should automatically be displayed as was saved.

[devgianlu]

I'm having issues with the dark theme, and I don't really know how that would look like. Also the idea of having custom themes for each component is a bit pretentious and not very feasible.

@mgagemorgan