Miscellaneous dashboard fixes.

- Increased plugin name width on health index.
- Decreased with of row labels for small screens on termination report.
- Added spinner for first page load.
- Changed switch logic to set embed class sooner.
- Fixed bad reference to SandboxesAdapter singleton on sandboxes index.
Merge pull request #479 from mozilla-services/features/misc-dashboard-fixes

Miscellaneous dashboard fixes