versionsByProtocolVersion index (complement versionsByMinecraftVersion index for protocolVersions lookup)

[deathcap]

f01605f added protocolVersions support with the versions array and versionsByMinecraftVersion index, but looking up the version data by a protocol version would be useful in some situations. Note that since protocol version has two namespaces (usesNetty: true and usesNetty: false), there is protocol version overlap, but this could be solved by using negative integers for usesNetty: false and usesNetty: true.

Proposed use case: related ot PrismarineJS/node-minecraft-protocol#330 Intra-release multi-protocol support. In node-minecraft-protocol, could allow the version options to be either:

• typeof version === 'integer': use a version by protocol version integer (versionsByProtocolVersion index)
• typeof version === 'string': use a version by minecraft release version string (versionsByMinecraftVersion index)

Both indexes would allow looking up majorVersion to map to the minecraft-data 'dataset' (1.8, 1.9...). The Minecraft release version string is more human-readable, suitable for custom client/app development, and the protocol version integer is more programmatically useful for automatically passing from the ping packet for PrismarineJS/node-minecraft-protocol#331 dynamic cross-protocol support.

This index could be used in #13 Update to use minecraft-data for toMajor(), so these would be equivalent:

   require('minecraft-data')('1.8.9')
   require('minecraft-data')(47)

(but accessing these indexes may require #14 Lookup protocol data at top-level of module?)

[rom1504]

I actually did that before commiting f01605f but then I noticed that there are multiple versions for a single protocol version (for example 47 has lot of versions), which one should we return ? all of them ?
About pre/post netty, I was thinking about just separating that index in two (preNettyVersionsByProtocolVersion and postNettyVersionsByProtocolVersion), a bit like what's been done for mobs and objects.

[rom1504]

I'm going to return all corresponding versions. For toMajor, I guess I'll just pick the first one. Currently the mapping protocolVersion -> majorVersion is unique anyway.

[rom1504]

Released as 0.19.0