Post-v1.5 UX improvements

[zephod]

Various UX improvements, bugs, and suggestions are collected here:

• [general]: Empty tables have a '(none)' placeholder which is causing issues. Move it into a separate div - it doesn't need be a wide <td> object.
• [dataset/edit]: Errors in form - would be nice to auto-open the appropriate resource box.
• [search]: Declutter the sidebar. No yellow box.
• [search]: Facets to go on the left, rather than the right. More logical flow.
• [dataset/edit]: No hint is given that the time format for a resource is in ISO, eg 2005-01-01T10:10:10