Encode user input before insertion into URLs

Encode user input before insertion into URLs

Encode user input strings used to formulate URLs, to ensure they do not
cause the structure of the URL to be subverted.

Task-number: QTBUG-19925
Change-Id: I6173f4df67a4bc1676ac32be6072763fc16f9720
Reviewed-by: Martin Jones <martin.jones@nokia.com>