various tweaks bug fixes, improvements and additional nodes

-- Fixed undiggable injector
-- Rewrote some of the quarry (puhfa: rewrote the dig functions to to
use voxelmanip, also removes a row of nodes at a time instead of 1 node
at a time, this allows us to raise the abm interval.  crazyR: added the
option to scrap cobble before it reaches the inventry/tubes, updated the
formspec.)

-- Added a check in quarry, lasers and drills, so that it does not dig
nodes with the group: "admin_node" usefull for jail mods and admin nodes
that should not be digable by the average player.

-- redesigned the quarry texture

-- Created a admin power node, generates same amount of power as a
reactor, does not require fuel. is only aquired via the give/giveme
comand.

-- Nuclear reactor  now melts down upon failed structure check.  if the
reactor melts down, the water is removed and the core turns to a lava
source. also the abm no longer checks all nodes of the reactor structure
every global step as that is a waste of reseources. (many loops checking
729 nodes every ~second)

instead the reactor check all nodes on startup, then after that is check
1 node at random on each global step.