Reload local dependencies to interpreter on restart if the library has changed

If user specifies library path in interpreter dependency setting, even when the file on this path is updated, new file doesn't take effect on interpreter restart but does only when user clicks Edit -> Save.

The mechanism of dependency loading is copying all dependency libraries under local-repo/

{interpreterId} and add these directory to classpath of interpreter process. Zeppelin copies these dependencies either on Zeppelin startup or dependency saving/editing.

Zeppelin should check if the library on specified local path is updated, and copy them to local-repo/{interpreterId}

on restart if it was.

Here is the bug report on users mailing list
http://apache-zeppelin-users-incubating-mailing-list.75479.x6.nabble.com/Dependency-jars-not-refreshed-after-interpreter-restart-in-Zeppelin-0-6-1-td4035.html