Change popup h2 color from orange to gray.
Show message in popup when no tabs are marked.
Show favicon in visualization page.
Change CSS and add help for visualization.
Change and document hypertree node actions.

Left clicking on a tab node switches to the tab. No need for displaying
the arrow now.

Tab nodes cannot be focused. Focusing was not producing a useful view
anyway. Other nodes can be focused on left clicking.

Actions are shown in the tooltips. Overall instructions are shown in the
visualization page.

No more animation of nodes on hover. Animation was causing problems with
centering and the subsequent layout turned out to be garbage. Removing
the animation at least keeps the important tree behaviour correct.
Add more documentation in all pages.
Update help file.
Add actions in context menu to right side panel.
Update tab title in panel on mark/unmark.

Also fix marking issues arising from tab ID being passed as a String
instead of an int.
Focus fake nodes correctly from panel.