Plugin node

[rilendorf]

Pluginapi to overwrite node interactions
Use cases: obvious

Please keep in mind that this is not finished yet, I just want to have it as a PR to discuss

[HimbeerserverDE]

Mark it as ready for review when you're done.

[rilendorf]

This aims to overwrite node interaction for specific nodes, specified by Itemstring.

This is done by...

• implementing a BlkData Handler to handle ToCltBlkData packets using RegisterBlkDataHandler
• implementing a itemstring -> nodeid / param0 cache for specific nodes (RegisterCacheNode)
• and then by handling interact packages and checking if the node interacted with is registered by some NodeHandler.

Some other functions that are a thing:

• GetMapCache which returns a copy of the map cache (map[[3]int16][4096]mt.Content)
• IsCached which returns true, if a node is cached
• RegisterCachedNode which tells the ms to save when the specified itemstring is defined
• GetNodeId which returns all nodeid's corresponding to a cached itemstring (map[mt.Content]bool)