#16: Manifest entry "Archiver-Version" is incomplete/wrong

Entry does not reflect the archiver version. Remove since it adds not information it pretends to add.

This closes #16

Author: michael-o

src/main/resources/org/codehaus/plexus/archiver/jar/defaultManifest.mf

@@ -1,3 +1 @@
 Manifest-Version: 1.0
-Archiver-Version: Plexus Archiver
-

src/test/java/org/codehaus/plexus/archiver/jar/ManifestTest.java

@@ -191,13 +191,11 @@ public void testGetDefaultManifest()
     {
         java.util.jar.Manifest mf = Manifest.getDefaultManifest();
         java.util.jar.Attributes mainAttributes = mf.getMainAttributes();
-        assertEquals( 3, mainAttributes.size() );
+        assertEquals( 2, mainAttributes.size() );
         assertTrue(
             mainAttributes.containsKey( new java.util.jar.Attributes.Name( "Manifest-Version" ) ) );
         assertTrue(
             mainAttributes.containsKey( new java.util.jar.Attributes.Name( "Created-By" ) ) );
-        assertTrue(
-            mainAttributes.containsKey( new java.util.jar.Attributes.Name( "Archiver-Version" ) ) );
     }