RFC: delete icon on activity thumbnail on every activity (except current active one)

[Thomas Pfeiffer]

> is it now in master.
> however the delete button continues to be disabled for the other
> thumbnails to
> prevent accidental triggering

What sense does it make to show disabled buttons? We wanted to
enable the user to delete an activity without scrolling to it before.
Disabled buttons would only irritate users even more...
We should enable those buttons and test a bit. If it turns out that
accidental triggering happens so often that it's annoying, we remove
them again. But please don't introduce disabled buttons.

Thanks,
Thomas