Support for versioning the configuration files

[t2gran]

Motivation: In a larger deployment it would ve nice to support versioning the OTP configuration and to be able the query the version from the APIs.

1. Let each of the configuration files contain an optional version property. The deployment environment could then inject the propper version string in each of the config files(otp-config.json, build-config.json and router-config.json).
2. The version number would then be available for logging and as info on the APIs.
3. On the TransModel API this info fit in the ServerInfo call.

Version of OTP used (exact commit hash or JAR name)

dev-2.x

Router config and graph build config JSON

// otp-, build- and router-config.json
{ 
  "version" : "<Version number injected by the CI/deploiment pipline>"
}

Transmodel API

type ServerInfo {
    :
    "The build-config used when building the transit graph. Note! This is not necessarily the same version used to build the street-graph." 
    buildConfig : ConfigInfo
    "The router-config loaded by the current running instance used for all routing requests." 
    routerConfig : ConfigInfo
}
type ConfigInfo {
    version: String
}

[t2gran]

"configVersion" is maybe a better name.