[pcp] pmdagfs2: documentation updates

[Paul Evans <pevans@xxxxxxxxxx>]

Hi,

I have adding some documentation in the usual places for pmdagfs2, these 
include a man page, a readme file along with additional commenting in 
the qa test files. Any feedback on these would be greatly appreciated.
These changes are available at: git://github.com/pauljevans/pcp.git dev

Looking forward I plan on making some changes to the qa files to have 
better guarding for configurations that are not set up correctly 
(checking debugfs is mounted etc.) and moving towards providing a client 
application to bring together pmdagfs2 metrics for all nodes of a given 
cluster. Some additional metrics are on the cards too.
Cheers,

Paul