Add support for additional heavy weight resource

[chlue]

While I really like to be able to jump to already visited places I find the drives too powerful once you figure out some abusive methods to use them (e.g. accelerate a light high delta-v beacon probe. Jump refuel vessel to probe and refuel, brake probe into target orbit)

So my proposal is to add an additional heavy weight 'jump charge' resource. This could be implemented by giving the FTL drives an converter to convert ore to 'jump charge' maintaining the mass of the ore. Each jump then cost the same mass in 'jump charge' than the remaining vessel mass. So basically some constant price to pay for 'tearing up space'.

Due to the very bad mass fraction of the ore tanks the drives should be able to store enough 'jump charge' to do at least two jumps with reasonable sized crafts (would actually give you a good reason to stack drives to enhance 'jump charge' storage space on heavy crafts too) in order to be able to do round trip missions (75% of the craft mass needs to be 'jump charge')

This addition would still allow round trip jump mission and don't really affect the indented usage, but avoids abusing the drives to zap around all the time and make beacon probes as outlined above impractical because now the heavy mass is in the tanker so one can better build a proper beacon directly. Additionally a nice supply mechanic from ISRU operations would be added.

[linuxgurugamer]

I may add an additional variable to the calculations, related to the difference in speed, but not specifically this