Allow setting loader_type via script on existing loaders

[Nexela]

Allow setting loader type via script on existing loaders. This will allow mods to change to either input or output without having to destroy and replace the loader.

[bobingabout]

The main reason why my mod doesn't even add loaders, is because I could never figure out how to make them load a chest.

[Nexela]

Loaders are very similiar to undeground belts in that they have an "input" and an "output" and a direction. The flat "non belt" portion is where it will put or pull stuff from from. and the input or output (arrows) let you know if it is in input or output mode.

After a loader is placed "rotating" changes the input/mode mode but doesn't actually rotate the entity just like underground belts.