Merge branch '7.x' of github.com:Islandora/islandora into 7.x
added management of deleted files
added deleted object management
fixed hook name
updated constant name
reverted constant
codesniffer changes
coder changes
removed unavailable code
removed return statements
removed return statements
added constants, redefined menu path
converted to sparql - itql was getting messy
changed function names to avoid future name collision
return labels from content models
Add response headers.

... Still need to react to requests.
Implement the HTTP cache validation shenanigans.
Force cache revalidation.
Coding standards.
Code standards, again.