Changed C6 to a6 (and updated support)

This is necessary because the C6 would return
6 array elements, while a6 returns a single element
of 6 bytes, which is what we want here.
Multiple changes to Packet:

Don't use a child hash of header
Don't store the payload (return it instead)
Allow for packed types
Added GetChannelAuth IPMI call and tests
Silly file rename
Added Application Response as a header type
Response was not ready to be added, removing
Created a super class for Request (and Response)
Added a Response child class to Message