Allow engine signatures in gamedata

[iekaslo]

Hello.
Signatures that are requested from the engine library cannot be found and used without explicitly specifying binaryPath where the absolute path to the libengine2 library will be written.

"signatures": {
	  "library": "engine",
          "linux": "\\x55\\x22..."
          "windows": "\\x55\\x22..."
}

[Nexd]

yeah, I've only adjusted the code to allow passing arbitrary binaries to the internal managed functions but did not touched gamedata related parts, should be an easy fix