Plnimportercommand

Refactor the two import commands.  

 * The plugin import no longer needs to unzip the jar files to get the manifest and plugin.xml files - php can do that from inside the .zip file. 
 * Removes the foreign key from content providers to plugins - it belongs in content owners.
 * Create the key from content owners to plugins. Owners are now created as necessary during import.
 * Drastically improved memory management - importing 60,000 aus from the XML file now takes less than 100Mb of RAM.
 * Add caching to the titles import commands for performance improvement. 

This PR isn't really 105 commits. Only the commits from October 31 and on are part of it. I'm not sure why it's so strange, probably something to do with rebase vs. merge.