Split GTK GUI task tracking and thread cancellation
Add support for setting thread names for asynchronous search
Use distinguishing thread names

 Like this multiple search threads might be running and can be individually cancelled
Add a read-only threadName property
Return provider name for asynchronous address searches
Add a simple text button with colored background and rounded corners
Add  address search in progress information item

The information item only shows up once the search is in progress and shows both search progress and also a cancel button that can be used to cancel the search.