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

[Fania Bremmer]

** Proposed Change **
Show the delete icon of activity thumbnail on every activity in the 
wheel (except currentty active activity)

** Reason For Change **
Currently only the activity thumbnail in the middle gets the delete 
icon. Before any activity thumbnails showed the delete icon; in my 
opinion this was easier to understand, if searching for a delete 
function. Now the possibility when to delete is very limited. We should 
only exclude the currently open activity because of refresh problems.

** Implementation Details **
- show it on every thumbnail exept for the currently open activity