[HACK-3252] add create/delete disk functions

This pull requests resolves Issue #20 

Creates two new functions:
Hardware.addDisk(size)
Disk.delete()

 This is a HACKATHON ticket.

https://dataxu.atlassian.net/browse/HACK-3252
If an assert fails before this is hit, will the config get deleted? Probably better to use a test case teardown to ensure it does.