C2S: offerTicketC re-enabled and supporting looms and remote origin repo

What's missing:

- Match patch VCS, origin repo VCS and target repo VCS
- Hook into postPersonInboxR
- If only origin is provided, generate patches / otherwise somehow remember the
  commits proposed

th/models

@@ -415,9 +415,9 @@ TicketParamClass
 Ticket
     number      Int           Maybe
     created     UTCTime
-    title       Text                -- HTML
-    source      Text                -- Pandoc Markdown
-    description Text                -- HTML
+    title       Text
+    source      PandocMarkdown
+    description HTML
     status      TicketStatus
     discuss     DiscussionId
     followers   FollowerSetId