Update plugin test framework to junit5

Updates the testing infrastructure to use the latest relesae of junit and
leverages the new extension mechanism to create an easy to use testing
framework.  Also adds additional test coverage for several plugins.

game/plugin/api/src/player.kt

@@ -29,30 +29,28 @@ val Player.runecraft: SkillProxy get() = SkillProxy(skillSet, Skill.RUNECRAFT)
 /**
  * A proxy class to allow
  */
-class SkillProxy(val skills: SkillSet, val skill: Int) {
+class SkillProxy(private val skills: SkillSet, private val skill: Int) {
 
     /**
      * The maximum level of this skill.
      */
-    val maximum = skills.getMaximumLevel(skill)
+    val maximum: Int
+        get() = skills.getMaximumLevel(skill)
 
     /**
      * The current level of this skill.
      */
-    val current = skills.getCurrentLevel(skill)
-
-    val experience = ExperienceProxy()
+    val current: Int
+        get() = skills.getCurrentLevel(skill)
 
     /**
-     * A proxy class to make [experience] (effectively) write-only.
+     * The amount of experience in this skill a player has.
      */
-    inner class ExperienceProxy {
-
-        operator fun plusAssign(amount: Int) = skills.addExperience(skill, amount.toDouble())
-
-        operator fun plusAssign(amount: Double) = skills.addExperience(skill, amount)
-
-    }
+    var experience: Double
+        get() = skills.getExperience(skill)
+        set(value) {
+            skills.setExperience(skill, value)
+        }
 
     /**
      * Boosts the current level of this skill by [amount], if possible (i.e. if `current + amount <= maximum + amount`).

game/plugin/api/src/util.kt

@@ -1,8 +1,8 @@
 package org.apollo.game.plugin.api
 
-import java.util.Random
+import java.util.*
 
-val RAND = Random()
+public val RAND = Random()
 
 fun rand(bounds: Int): Int {
     return RAND.nextInt(bounds)