tox: Always notify "status-message" and "name"

Notify the old value if toxcore failed to set the new one, otherwise the
entries in the me-popover used to change the values will keep the
strings that failed to be set.
transfers: Don't automatically accept transfers

Implement UI to accept incoming file transfers and choosing a download
location. The user now has to confirm incoming transfers by clicking the
'start' button in the transfer row, which opens a 'Save as' dialog. Once
a destination has been chosen the file transfer will accepted and
started.