Rename Vool to Sol

Simple is really the descriptive name for the layer
Sure, it is "virtual" but that is not as important as the fact that it is simple (or simplified)
Also objct (based really) is better, since orientated implies it is a little like that, but only orientated, not really it. Sol only has objects, nothing else
Just cause i was renaming anyway

test/sol/test_ivar.rb

@@ -0,0 +1,32 @@
+require_relative "helper"
+
+module Sol
+  class TestIvarSlotMachine < MiniTest::Test
+    include SolCompile
+
+    def setup
+      @compiler = compile_main( "@a = 5")
+      @ins = @compiler.slot_instructions.next
+    end
+
+    def test_array
+      check_array  [SlotLoad, SlotLoad, ReturnJump, Label, ReturnSequence ,
+                    Label] , @ins
+    end
+    def test_class_compiles
+      assert_equal SlotLoad , @ins.class , @ins
+      assert @ins.left
+      assert_equal :message , @ins.left.known_object
+    end
+    def test_slot_gets_self
+      assert_equal :receiver , @ins.left.slots[0]
+    end
+    def test_slot_assigns_to_local
+      assert_equal :a , @ins.left.slots[-1]
+    end
+    def test_slot_assigns_something
+      assert @ins.right
+      assert_equal SlotMachine::IntegerConstant ,  @ins.right.known_object.class
+    end
+  end
+end