Breaking Changes:

* Updated to Minecraft 1.15.1
    * A lot of rendering methods changed to take a MatrixStack plus a
      VertexConsumerProvider for rendering.
* FluidExtractable is no longer a valid functional interface.
    * While it was never annotated with "@FunctionalInterface" it used to be 
      possible to use it as one, however it no longer is due to the non-breaking
      change requiring the 1620-based method to still exist, and default-call
      the FluidAmount based version. (Which calls the 1620-based one for compat).
    * If debug checks are enabled (which they are by default) then either will throw
      an exception if the class hasn't overriden at least one of them. 
* Changed the return type of "FluidInsertable.getMinimumAcceptedAmount" from an
  integer to a nullable FluidAmount.
* Renamed "FixedFluidInv.getView" to "getFixedView",
  and "GroupedFluidInv.getView" to "getGroupedView".
    * This is to allow a single class to implement both, without needing
      to redeclare the method with a custom return type.

Changes:

* Moved over from base-1620 fluids to fully fractional fluids.
    * Added a new class "FluidAmount" which stores the fractions as
      long + (long/long).
        * A lot of new methods have been added for operations.
    * This means that a lot of 1620-based functions have been deprecated
      and new functions have been added that take or return FluidAmount
      instead of int.
    * If you want to display a FluidAmount to the player you should use
      FluidAmount.toDisplayString(), which returns a string like "1.34712".
      (as opposed to "toString()", which returns a string like
      "{FluidAmount 5 + 62/85} for debuging").
    * You can turn a String into a FluidAmount with FluidAmount.parse() or tryParse().
* Changed the meaning of Fluid(Key/Volume).get(Still/Flowing)Sprite:
  now it is no longer recommended that you use them and always use
  the FluidVolume.getRenderer, because the renderer will handle fluids
  with special rendering correctly (like the enchanted item glint for potions).
* Deprecated ImplicitVanillaFluidVolumeRenderer as DefaultFluidVolumeRenderer
  now includes all of it's logic.   

Additions:

* Added RebornCore fluid compatibility.
* Allowed defining a fluid key that is only identified in
  a Map<Identifer, FluidKey> rather than only allowing fluid
  key definitions to come from a minecraft registry. 
* Added gaseous, cohesion, viscosity, density, and thermal capacity properties
  to FluidKey. Everything except gaseous (which is a boolean) is of type FluidAmount.
    * Water has a value of 1 for all of these properties, and lava is based around that. 

Bug Fixes:

* Fixed block attribute lists not obstructing entries correctly.
