Feature/utm coordinates

[lukasgolson]

This PR adds the feature request from #77.

• Adds config options to realm schematics to set the UTM zone and eastings/northings of the realm at origin -- local pos: (0,0).
• Adds a command to set the UTM zone and Eastings/Northings values of any existing realm.
• Adds a function to convert from UTM to lat/long pairs
• Adds a toggleable HUD to display player position in either world space, local space, grid space, UTM space, or Latitude/Longitude pairs.
• Adds a realm data command to set and retrieve the arbitrary realm storage values added onto realms
• Added UTM info to the MKRF config files

[lukasgolson]

Here is an example set of UTM Zone 10N coordinates (in units of meters) to work with for all of the MKRF512 maps:

• Top (north of map): 5,464,756
• Bottom (south of map): 5,464,244
• Left (west of map): 533,244
• Right (east of map): 533,756

Note that Top - Bottom = 512 and Right - Left = 512, which are (x,z) the dimensions of the world (exclusive of the map barrier). If we include this information as optional input in the map.conf file, then we only need a single pair of tie coordinates (e.g., Top/Left or Bottom/Right) in order to define any other UTM coordinate in the map. The above coordinates are at the center of those nodes at the defined (x,z) position, not the edge, so keep in mind when doing calculations, otherwise the calculations will be off by 0.5 m.

Hopefully this isn't a silly question, I have poor spatial understanding. I was thinking about this issue. Because all coordinates in the realm system, Minetest, and schematics are aligned at the center of the nodes, would the calculations still be off by 0.5m?

[pauldpickell]

In that case, there should be no issue. Just wanted to flag that the local UTM coordinates should be calculated from node centers.