Issue #215 Show Input plugins on the dashboard

- Only the Input plugin names will be displayed since they have no default data
- Dashboard cleanup
  - Add a path to the plugin URL so plugin pages containing a colon can be fetched
  - Fix the sort order on numeric fields
  - Remove the sandbox specific columns since the data is now available on the plugin page
Merge pull request #252 from mozilla-services/issue_215

Issue #215 Show Input plugins on the dashboard