Realistic Fluids Overhaul compatibility and rainfall fork

Other changes:

1. Now has a config file that matches the mod name. (RealisticFluids)

2. Saves the flow enabled state as a global in the config file; can be set from in-game command. Should only require single player or elevated server privilege.

3. Faster, less spammy. On my machine, it can handle 40K fluid updates at a time without slowing the tick rate, when not raining.

4. EnableFlow now supports tab completion and proper checking for success. Should even work from a command block now.

5. /enableflow renamed as /rff-enableflow, with an alias to /enableflow. Other commands will have the /rff- prefix.

6. Ocean no longer drains as you unload/load chunks; let me know if this is a "bad" thing. (Rainfall down, plus no more random disappearance, may be too much water).

7. Approximately one block in from the shore will get wet during rain.

8. All references to Block.Air should be changed to isAir/isAirBlock for mod compatibility.

9. ConcurrentHashmaps/ changed to ordered LinkedHashMaps; similar for Concurrent queues. We don't have concurrency, we don't need to pay the price. Ordered sequencing should prevent any unevenness.

10. Equalizations disabled; they seem to just make the sea less even.

11. ** All flow cases (flowing over snow, plants, etc) should match vanilla behavior. Please report anything that does not.

Known issues:

1. /Deflood not yet updated.

2. No commands for updating flow radius or sea levels yet.

3. Rain can be "stuck" in the air if the chunk is unloaded; top blocks in new chunks do not get awoken.

4. Still does not save fluid data or "to update" data when chunks unload.

5. Nether is slow.

6. Diagonal flow is still active.

7. Flow range/results from a bucket in a trench is not good enough yet.

8. Flow is not a function of the dimension-specific tick event, so forge does not see the time spent.

In particular, /forge tps reports meaningless numbers.

9. Nether is still slow.