Web PVR: When the description column for a result is clicked, open the info page in a new tab.

Otherwise, the position on the original page is lost for at least some screen reader users when they try to go back to it.
Fixes for 2c381ae9c08a8a55cc84dbb05a86e66548315976

Close #103
Web PVR accessibility improvements

- Expose the Apply Settings and Save As Default buttons as buttons (instead of just text).
- Associate labels with options single check boxes, popups and text fields.
 - Associate labels with options check boxes.
- Add ARIA landmarks for easier navigation.
- Mark some layout tables as presentation only. Without this, the title of the options_embedded table was repeated by the NVDA screen reader for every option. The searchhead table was treated as a real table, making navigation in the parent table very awkward.