Autolathe revamp and sub-menus for fabricators

* Updated the autolathe to use the datum/designs system (_new file autolathe_designs.dm_)

I'm planning to unify the _autolathe_, _protolathe_, _circuit_printer_ and _mech_fabricator_ under a ```/obj/machinery/fabricator``` subtype to reduce the snowflake, but i'm commiting this while there's no (more) conflict.

So, there may be some rough edges or unfixed already present bugs (sheets ejection amount when deconstructing comes to mind).

* Added categories sub-menus for the _autolathe_, _circuit_printer_ and
_protolathe_...

That should make R&D construction much less _tedious_.

__Mandatories images :__
![proto](https://cloud.githubusercontent.com/assets/7117411/5425640/aefa30ce-8320-11e4-8721-cef875819bbe.png)
![circuit_printer](https://cloud.githubusercontent.com/assets/7117411/5425639/ad19bd7e-8320-11e4-89c7-04006aa23d82.png)
![auto](https://cloud.githubusercontent.com/assets/7117411/5425638/a88d1a12-8320-11e4-9249-3e19cf0576a0.png)

__Note :__ categories are _suggestions_, changing them/adding others would take almost no effort, thanks to the new datum/design system.

* Fixes #6362