Multiproject builds

Multiple plugins can be aggregated by one project.

• Enable the AggregatePlugin on the aggregating module.
• Assign the plugin projects to Bukkit/serverPlugins and Bungee/serverPlugins.

val commonSettings = Seq(
  Bukkit / serverVersion := "1.12.2-R0.1-SNAPSHOT",
  Bungee / serverVersion := "1.12-SNAPSHOT"
)

lazy val root = (project in file("."))
  .enablePlugins(AggregatePlugin)
  .settings(commonSettings)
  .settings(
    Bukkit / serverPlugins += helloBukkit,
    Bukkit / serverPlugins += helloBungee
  )

lazy val helloBukkit = (project in file("hello-bukkit"))
  .enablePlugins(BukkitPlugin)
  .settings(commonSettings)

lazy val helloBungee = (project in file("hello-bukkit"))
  .enablePlugins(BungeePlugin)
  .settings(commonSettings)