*8798* Fix TinyMCE cache file when a single OJS install hosts multiple journals...

... with different base url paths by adding the baseurl to the hash.
Correct, it looks like everything is relative; there are currently no journal-specific settings, so it's strictly a matter of making sure the base URL in the TinyMCE config file is reachable regardless of the base path. I've commented on bug #8797; let's see about clearing that up first.