Filter Wizard: use consistent spacing for assignments

Signed-off-by: Tim Harder <timothy.harder@analog.com>
Filter Wizard: change the connect button according to various connection state

This should help users determine their connection status to a device via
libiio and also restrict them from reconnecting to the same device over
and over when they're already connected.

Signed-off-by: Tim Harder <timothy.harder@analog.com>
Filter Wizard: renable the connect to target button when IP is altered

Signed-off-by: Tim Harder <timothy.harder@analog.com>