Speed update of pressureplates up by using node_timers

Fix a bug (in some cases the output rules of a receptor weren't respected, bug introduced by commit before, 64d109b3)

`mesecon:updatenode()` was written to work only with conductors, though in several places it was used on recepters and effectors. This issue, reported by simion314, is fixed in this commit by explicitly checking for the type of mesecon node being updated.

tile_images modified tiles

* not obtainable legitimately in Survival mode
* found in Creative inventory or using /giveme mesecons_commandblock:commandblock_off
* glows slightly when turned on
* runs a command in the context of the targeted player
* player can be targeted by name, or using the special forms (@nearest, @farthest, @random)
* when powered, runs its command with its parameters
* right click to bring up the configuration screen
* diggable and modifiable only by its owner, the person who placed it

Use add_node since place_node only works with ItemStacks and can't specify param1/param2 value. This fixes pistons pushing pistons/torches/etc.

Further piston improvements, the pistons now delay before retracting and play nice with invalid states.

New pistons activation mechanism, fixes many of the issues reported when pushing mesecons around. Side effect is that it might be somewhat slower, and it waits a tiny delay before extending or retracting. This should be unnoticable in normal use.

Add ghoststone, crafted like removestone, with steel ingots at the corners. Trapstone disappears upon mesecon signals, but unlike removestone, reappears after the mesecon signal turns off.

fix t-junction selectionbox when on (was node-sized)

https://github.com/Jeija/minetest-mod-mesecons

insulated crossed wire

Implement mesecon:register_receptor(onstate, offstate, rules, get_rules) and make add_receptor_node(_off) deprecated

Gates

and microcontroller rules