Fix proto for rust march update

[JulianMa]

The recent rust update broke compatibility with the existing proto file.

The absence of certain fields when they have their default value, makes it seen, like FP switched to
proto3:

queuedPlayers: 0 -> field not present (https://github.com/alexemanuelol/rustplusplus/issues/410)
currencyIsBlueprint: false -> field not present (https://github.com/alexemanuelol/rustplusplus/issues/409)
Monument.x: 0 -> field not present (https://github.com/alexemanuelol/rustplusplus/issues/408)

In Proto3, missing fields in the response, which are required by proto definitions, are treated as they have their default values set. So receiving (queuedPlayers missing):

AppInfo {
    name: 'Random Server',
    headerImage: '...',
    url: '...',
    map: 'Procedural Map',
    mapSize: 4250,
    wipeTime: 123123,
    players: 100,
    maxPlayers: 120,
    seed: 123123,
    logoImage: '',
    nexus: '',
    nexusZone: ''
  }

will be evaluated as if queuedPlayers: 0.

By simple migrating the proto file, every message i received so far could be parsed without issues.
This just removed the required annotation on each field + sets proto3 as version.
WARNING: Enums are required to be 0-based in proto3. I wasnt sure how facepunch is handling this, so i for now introduced a RESERVED enum value for AppEntityType and EntityType. This is not tested yet, and this can break stuff, when facepunch decided to move the existing enums from

enum AppEntityType {
  Switch = 1;
  Alarm = 2;
  StorageMonitor = 3;
}

to

enum AppEntityType {
  Switch = 0;
  Alarm = 1;
  StorageMonitor = 2;
}

Just comment when your alarm is acting like an switch :)

[JulianMa]

will test later if Switch equals 0 or 1 in the actual server response

[JulianMa]

Can confirm, switches work