Mod for: https://mods.factorio.com/mod/Transport_Drones

Support for:
* https://mods.factorio.com/mod/bobelectronics (uses basic circuit board)
* https://mods.factorio.com/mod/pyhightech (uses simple circuit boards)
* https://mods.factorio.com/mod/pypetroleumhandling (uses small parts in recipes)
* https://mods.factorio.com/mod/aai-industry (replaces drone-engine-unit with electric-motor)

Refine coal (later petrogas and rocket fuel) to drone fuel to be used with Transport Drones.

Moves the tech requirements for drones to the start of the tech tree to get started quicker.

Removed steel requirement from everything, hopefully balanced with higher iron costs.

Replaced engine in drone recipe with drone cylinders.