gaxis -add some gremlin plot controls

zoom, view. and dro/offset controls
gladevcp -hal_actions home, unhome, MDI should be sensitive to states

while powered off and estopped de-sensitive the buttons as one can't use them
gladevcp -have hal_actions (eg MDI) check for is_all_homed state

can't use MDI if not all_homed, so desensitize the button
gladevcp -have hal_mdihistory widget check for machine states

can't issue MDI commands if not all homed or not powered or if estopped.
De-sensitixe if so.