Good keyboard navigation support in pages

[rpominov]

Keyboard navigation in pages list should work similarly to the navigator.

It doesn't work currently, because we use TreeNode instead of Tree to render the pages list (Tree supports D&D and keyboard navigation, but we don't want D&D yet)

Need to do one of these:

1. Switch to Tree ( depends on: #403 )
2. Decouple keyboard navigation from Tree
3. Decouple D&D from Tree

[kof]

I think we need d&d on it anyways