adding linux client support

[Ventilador]

Current Behavior On linux:

1. Without running the patcher, nothing really happens, the game loads as if nothing was done
2. After running the original patcher:
   An error occurs trying to load the Stationeers.Addons.dll saying basically that Assembly.LoadFile requires an absolute path (this is code generated by cecil, also this happens inside the game, in the F3 console)

New Behavior:

1. Without running the patcher, nothing really happens, the game loads as if nothing was done
2. After running the new patcher:
   Starting the game now shows 2 loading bars (for the Loading scene, removing prefabs, etc), not sure why.
   Once on the menu the addon compiles the plugins (the progress bar is shown in the menu)
   Loading a world should load plugins installed (tested with network painter)

What this change does:
It Path.Combines the runtime Environment.CurrentDirectory (meaning while running the game), and with the Stationeers.Addons.dll to get the full path.

It also copies all the required assemblies (from Stationeers.Addons project) to the rocketstation_Data/Managed folder, which seems to be auto loaded be mono, so all dlls there become available to the mods