Move OperatingSystem.ky from under the java plugin to top level.

Since Operating System class will be used by all plugins, it was
preferable to have it in a top level package accessible by all plugins
instead of just the java plugin.

This is part of a bug where the Jvm and JavaInfo also needs moving to
top level packages.

src/main/kotlin/com/beust/kobalt/OperatingSystem.kt

@@ -1,4 +1,4 @@
-package com.beust.kobalt.plugin.java
+package com.beust.kobalt
 
 import java.io.File
 import java.util.*

src/main/kotlin/com/beust/kobalt/plugin/java/JavaInfo.kt

@@ -1,5 +1,7 @@
 package com.beust.kobalt.plugin.java
 
+import com.beust.kobalt.OperatingSystem
+
 import java.io.File
 
 abstract public class JavaInfo {

src/main/kotlin/com/beust/kobalt/plugin/java/Jvm.kt

@@ -2,12 +2,13 @@ package com.beust.kobalt.plugin.java
 
 import com.beust.kobalt.misc.KobaltLogger
 import com.beust.kobalt.maven.KobaltException
+import com.beust.kobalt.OperatingSystem
 import java.io.File
 import java.io.IOException
 import java.util.HashMap
 
 public open class Jvm constructor(
-        val os: com.beust.kobalt.plugin.java.OperatingSystem,
+        val os: com.beust.kobalt.OperatingSystem,
         var javaBase: File? = null) : JavaInfo(), KobaltLogger {
 
     private var _javaHome: File? = null