Refactor dCC slightly.

Add question dialog to DCC Chats.
Add question dialog to DCC Sends.
Remove unused method askQuestion method.

Change-Id: Iaf9f6ff679ea662df46b7da25d212d79097bd9bd
Reviewed-on: http://gerrit.dmdirc.com/3498
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Chris Smith <chris@dmdirc.com>