UK. Generic problems_clause for two-tier councils

Replace copy-pasted problems_cause declarations in Hart,
Oxfordshire, and East Sussex with a generic override in
UKCouncils.pm

After https://github.com/mysociety/FixMyStreet-Commercial/issues/603 I applied a basic patch to East Sussex with copy/pasted code.  This patch makes this generic, now that 3 separate UK councils have this issue.