Remove LAYOUT_HEADER, LAYOUT_FOOTER

[jtickle]

Remove this feature entirely from Layout since it duplicates behavior found in Block. Database update to find any set LAYOUT_HEADERs and LAYOUT_FOOTERs, convert them to Blocks, which are set to show in the appropriate places.

[Stardog]

Layout will get a rewrite I believe and these will go away with it.