Action.c FIX / Rework / Clean-up Action System

FIX - softlock not allowing power button to shutdown device when active
FIX - autolock not working unless Selective backlight enabled

Rework - get_action_worker split into more managable chunks

Rework - moved all static variables to a single struct action_last
         to be passed through all internal functions

Rework - current action state moved to struct action_current
         to be initialized at each get_action /get_action_custom call

Rework - action lookup in button maps changed slightly to prefer fully formed actions
         rather than  blindly returning action with BUTTON_NONE as pre_button
         this should allow actions defined in keymaps positional independence

Rework / Clean-up - moved conditionals on internal functions to inside the functions
                  -Allows much cleaner code & empty functions should be optimized
                   out by compiler

Rework / Clean-up - softlock and backlight exemptions code

Clean-up - remove a lot of (now) unused defines

Clean-up - organize / move all exported functions to their own section in the file

Comments added to all internal functions to better explain their purpose

Change-Id: I0ac02d1a2b45826843611513fea3c20a819d2fed