genupdatejob: make sanitize a little more forgiving

Created by: rjw57

Initially we had to truncate video descriptions because the JWP client libraries would try to pass all parameters as GET requests, even when using HTTP POST. That has been fixed by later versions of the JWP client. Additionally, we want to allow for newlines in descriptions since they are usually important.

Update the sanitisiation function to only strip non-newline control characters and to no-longer truncate strings.