v3.0-alpha-2 for Spigot/CraftBukkit

Changes since alpha-1:

• Added support for v1.13.1 (v1.13 support is still present, but will be removed next release)
• Fixed missing textures for blue wool blocks
• Fixed redstone wire rendering in v1.13+
• Fixed door models in v1.13+
• Fixed huge mushroom rendering in v1.13+
• Fixed glass pane and iron fence models in v1.13+
• Fixed vine models in v1.13+
• Fixed prismarine stairs, slabs in v1.13+
• Fixed fence gate models in v1.13+
• Fixed broken cave rendering in v1.13+ (more than one type of air in v1.13...)

Note: this is respin of initial 3.0-alpha-2, as initial release had breaking issue with pre-1.13 Spigot. If you have problems there, be sure the release version shows as 'Dynmap v3.0-alpha-2-88'