Loads of fixes for API tool, styling, etc.

- changed landing page to link to new API tool instead of old one
- linked new API tool page from everywhere it wasn't already linked
- code boxes should double-click-to-expand in compiled rippled-apis page
- hopefully fix tracking on rippled-apis page?
- get rid of awkward shadow below code boxes
- get rid of awkward empty space above ripple-REST page's first header
- removed invalid </p> tag from end of several pages