Update README.md

Added additional instruction on issues opened on the tracker.
Move to assets lang system
Merge remote-tracking branch 'origin/BuildCraft-5.0.x' into BuildCraft-5.0.x
removed file added by mistake
changed biome ids in config, fix #1438
removed all references to EntityClientPlayerMP and fixed filler packet, fix #1437
fixed conversion error, fix #1439
added gradle-based build script
Merge branch 'BuildCraft-5.0.x' into builder