[#52224723] Update help text and display
[#52224723] Reject invalid Urls

Mainly to catch people who put other information in
there. But also optionally flag use of eg. internal
domains.
[#52224723] Transmit as policy URL
Resolve merge conflicts
Merge pull request #772 from JamesGlover/52224723_policy_text_field_should_be_url

52224723 policy text field should be url