Linux feature request: allow 'clear file' with sudo

[dia-susca]

When file permissions don't allow writing in a file by the user that executed klogg, the 'clear file' functionality simply does nothing (fails silently).
What would be nice is if klogg asked for the root password and execute the clear file as sudo. Editors such as Atom do that: a popup to authenticate with sudo pass is shown, and then the file is saved.
Thank you

[variar]

Somewhat related to #99