Setting claimability per node

I needed a way to choose whether individual nodes are claimable. The attached patch adds this functionality.

Each Content Type has a default (for this claimability setting,) and new nodes inherit their type's default.

This setting informs the logic that determines whether the "Claim Page Ownership" local menu item is available on a node. That logic now also ensures the the menu item is not displayed if the user already owns the node, and allows those with the permission to administer Claim Node Ownership to claim the node.

Permissions have been reworded a bit for understandability and with respect to the main change in this patch:

• 'admin claiming ownership' is now 'administer claim node ownership'
• and 'claim ownership' is now 'claim ownership of claimable content'

I plan to extend this module further and would be glad to maintain/co-maintain the module.