Add LongObjectHashMap and LongHashSet

Replace uses of LongHashtable and LongHashset with new implementations.
Remove EntryBase, LongBaseHashtable, LongHashset, and LongHashtable as they
are no longer used.

LongObjectHashMap does not use Entry or EntryBase classes internally for
storage so has much lower object churn and greater performance. LongHashSet
is not as much of performance win for our use case but for general use is
up to seventeen times faster than the old implementation and is in fact
faster than alternatives from "high performance" java libraries. This is
being added so that if someone tries to use it in the future in a place
unrelated to its current use they don't accidentally end up with something
slower than the Java collections HashSet implementation.

src/main/java/org/bukkit/craftbukkit/util/LongHash.java

@@ -1,6 +1,6 @@
 package org.bukkit.craftbukkit.util;
 
-public abstract class LongHash {
+public class LongHash {
     public static long toLong(int msw, int lsw) {
         return ((long) msw << 32) + lsw - Integer.MIN_VALUE;
     }
@@ -12,16 +12,4 @@ public abstract class LongHash {
     public static int lsw(long l) {
         return (int) (l & 0xFFFFFFFF) + Integer.MIN_VALUE;
     }
-
-    public boolean containsKey(int msw, int lsw) {
-        return containsKey(toLong(msw, lsw));
-    }
-
-    public void remove(int msw, int lsw) {
-        remove(toLong(msw, lsw));
-    }
-
-    public abstract boolean containsKey(long key);
-
-    public abstract void remove(long key);
 }