Minor issues with table view

[jonorthwash]

• There should be a keyboard shortcut for entering table view which should also enter table navigation mode (even if table view is already enabled). (moved from Minor issues with table view #333)
• Current cell should be highlighted. This is the case, but the style is impossible to see in the already grey cells. Perhaps a neon-coloured drop-shadow just inside the cell border would work? :)
• Should be able to just start typing (as in a spreadsheet) for editing, instead of having to click or press enter. I.e., always in edit mode.
• Likewise, arrow keys in edit mode (↓, ↑ whenever; →, ← after edges are reached) should navigate to new cells.
• Keyboard shortcut and UI way to add and remove rows.