Add basic index file reader/writer and basic test

src/test/java/net/runelite/cache/fs/IndexFileTest.java

@@ -0,0 +1,20 @@
+package net.runelite.cache.fs;
+
+import java.io.File;
+import java.io.IOException;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class IndexFileTest
+{
+	@Test
+	public void test1() throws IOException
+	{
+		File file = new File("d:/rs/07/test/test.dat");
+		IndexFile index = new IndexFile(5, file);
+		IndexEntry entry = new IndexEntry(index, 7, 8, 9);
+		index.write(entry);
+		IndexEntry entry2 = index.read(7);
+		Assert.assertEquals(entry, entry2);
+	}
+}