Begin site redesign.

Using Polymer to give it a similar Material Design feel to the LOOT v0.7
UI.

This commit is a bit messy because I just started playing around and
accidentally ended up with something I'd like to keep...
Remove extra title from docs page.
Reorganised nav sidebar.
Updated credits page.

Added progress indication for fetching contributors, moved CSS into
credits HTML file, and removed extra title.
Improved title text styling, removed dead CSS.
Slight title tweak to index page.
Fixed titles, closed elements in docs page.
Removed extra closing tag from credits page.
Search page styling improvements.

* Added spinner to progress indicator.
* Closed tags.
* Swapped input for paper-input decorated input.
* Progress indicator returns on second and later searches.
Fixed search scrolling going beyond window base.
Tweaked search controls layout.
Use <paper-dropdown-menu> for search game select.
Removed an unused style.
Restyled credits using Material Design ideas.

Each contributor gets a card, which is styled as a two-line list item
with an avatar, but the cards are displayed inline from highest
contributor to lowest.
Replaced core-icon-button with paper-icon-button.
Added Polymer dependencies via Bower.

So many files...