add unified interface for accessing file system

**please review**
I deleted it because I ended up not using it a while ago. The code as written had issues with the classloaders that meant that the two different classloaders used by the application didn't share classes from the k core. It made the code as written unusable and since I don't know anything about classloaders, I elected to make plugins be placed in the main application's classpath instead and use only a single classloader. I can put this in a separate pull request if you want because it's not really related, but it didn't seem worth the effort to me.