Added support for Prototech thrusters to be added to signatures at the same level as large hydrogen variants and also be locked to forward only thrust.
They do not have their color altered, however.

Added beta test of ship speed based control of Gravity Generators to (kind of) mimic thrust based gravity.
I opted for grid speed vs thrust for a better user experience over a more 'correct' approach.

The mod looks for any Gravity Generators on the grid and checks their custom names.
If the custom name has the character "+", positive Gravity Generator accel is added at speed.
If the custom name has the character "^" (ctrl+6), negative Gravity Generator accel is added at speed (for upside down gens in builds).
If you leave those characters out of the custom name for the grav gen block, you are opted out of this system.

If you want to use this system, please ensure that the Gravity Generator field is setup correctly with a little overlap.

Testing feedback is appreciated.

Added SciFi Ions to the thruster color mod.