Major change: Documentation is now included with mesecons, the website just extracts the documentation in a more readable format

This makes development of new features easier, as documentation can automatically be updated on the website without modifying the website's code!
Every mod that has nodes in the mesecons modpack has a "doc" folder that contains subfolders with recipe, description and preview of the block. The website will discover which documentation is available
by reading the documentation.json file.

Remove legacy code that enabled / disabled mesecon wires that were placed 2 blocks below a
pressure plate. From now on, please place a vertical wire at that place. That way, no false
signals will be triggered (the wire won't "flash" turned off if you enable it by a pressure
plate and turn off a switch connected to it).
If you depend on this functionality, please just revert this commit. That should be possible in
the near future as well, since no major rewrites are planned for mesecons_pressureplates. In the
long run, please update your mesecon strucutres to use vertical wires instead of relying on this
old hack.

Settings can now be retrieved by mesecon.setting(<name>, <default>) and can be modified without
editing the source code by adding the setting to minetest.conf
For instance, you can add mesecon.blinky_plant_interval = 0.5 to minetest.conf in order to
increase the blinking speed.
Rewrite the blinky plant with nodetimers.
Fixes #161

flexibility and because it was never inteded to be OOP in the first
place.

mesecon.receptor_on and mesecon.receptor_off are provided by wrappers
(mesecon:receptor_on/off) for compatibility, but will be removed. Mod
programmers that use mesecons: Please update!

Also, fix microcontroller polluting the global namespace and remove some
deprecated stuff.

wires 2 nodes below them, allows to hide circuitry powered by them.
Fixes #179
Rewrite pressure plates + vertical wires using mesecon.register_node.

Digging and footstep sounds for everything that needs them! Plus, pushing buttons, punching switches, and flipping levers all make sounds.

Port a lot more (basically everything apart from gates, pistons and extrawire crossing) to the new nodedef system. There are some problems with wall button and wall lever (in the way they visually connect to wires)

visibly connect to neighboring wires.