ENH: Move topic properties to separate table

Topic property values are stored in xml in "topicdata" column. Create a "topic properties" table and move each property value to separate row.

Context:

> @johnhenley it;s a long time ago. IIRC one thing was that you cannot remove a custom property once you created it

Hmm. That would make sense since property values are stored as an xml document in the topic table :(. So to remove a property would require unpacking and repacking every topic that has a property being deleted.

As I've moved through the modernization of the module, moving properties to separate data structures/tables has been something I've thought about doing. I can see properties being a very useful feature if they are more obvious and accessible.

_Originally posted by @johnhenley in https://github.com/DNNCommunity/Dnn.CommunityForums/issues/725#issuecomment-2049579696_