Add widget tooltips with channel name

[lulol]

Adds a tooltip with the channel/item/episode name to every flowbox button, not only to those showing ellipsis in their name.

Fix #227

[mtwebster]

Can you set this on the button, not the label - it's not really obvious that you have to hover over the text specifically (in fact I thought the PR was broken at first because of this).

Thanks

[lulol]

Since all items have a tooltip and not only those with ellipsis, and I expected that for those people naturally would point to the text to check for the missing part, choose to put the tooltip in the label because felt it was less annoying than having it show in all the buttons while browsing the list.

Hope you squash all these commits.

[mtwebster]

I did notice it could potentially get in your way when browsing but let's see (we can always switch back to just the labels).

Thanks