feature #2063: Add Custom hook to VM Pool.
(cherry picked from commit 1c4d369c3bc88befb3bc6e72eba68a2e8883ee99)
feature #2019: Adds PREV_STATE and PREV_LCM_STATE to hook attributes.
(cherry picked from commit 2d102df0c7fa6e457b2fe12ddc4141b0af924939)
feature #2019 and feature #2063: Add documentation in oned.conf(cherry picked from commit 7bc714cc5d6a8e65758a36d15ac5dccfa2acd6d1)