Medium: node: clear state new way since pcmk 1.1.8 (bnc#843699)

As of v1.1.8 cibadmin cannot remove node state. Switch to
stonith_admin -C for newer versions.
merge with upstream
Low: bnc#845336: Updated documentation to cover groups more extensively.

Group documentation now also includes information about containers.
Dev: Merged updated documentation
Medium: cibconf: fix two fencing top issues (savannah#40173)
merge with upstream
Doc: add the rsctest tutorial