RealFuels v6.0

Changelog:
v6 /
*Updated plane parts (C7, Firespitter) to have B9-esque levels of resources. No more magic volume-disapppearing tricks when fuel tanks become fuselages.
*Massive improvements from swamp_ig, for integration with Procedural Parts and other mods, and UI improvements.
+Switchable tanks
+fixed symmetry bug
+(optional) tweakable utilization
+Better integration support
+loading fixes
+Display GUI from tweakables
+SI units
*taniwha: show version on GUI
*support more Firespitter parts
*Update to ModuleManager v2.1.5
*Sandworm: support HGR tanks

NOTE: At this point it is recommended to switch from StretchyTanks to Procedural Parts (if you have not already done so).