Remove debug class

When in development, we have Kint to use instead.
Move the interfaces to their own directory

We can't use "interface" in the namespace, so we need to call them
contracts instead.
Update the catalog models

The QuickInstall interface changed slightly so the implementations of
the interface needed to be updated as well.
Cleanup the Markdown class
Update the class aliases
Add the media interface (WIP)
Add the media class (WIP)