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/ruby/test_assignment1.rb

@@ -1,30 +1,30 @@
 require_relative "helper"
 
 module Ruby
-  class TestVoolCallMulti2 < MiniTest::Test
+  class TestSolCallMulti2 < MiniTest::Test
     include RubyTests
 
     include RubyTests
     def setup
-      @lst = compile( "@foo = a.call(b)").to_vool
+      @lst = compile( "@foo = a.call(b)").to_sol
     end
     def test_class
-      assert_equal Vool::Statements , @lst.class
+      assert_equal Sol::Statements , @lst.class
     end
     def test_first_class
-      assert_equal Vool::LocalAssignment , @lst[0].class
+      assert_equal Sol::LocalAssignment , @lst[0].class
     end
     def test_first_name
       assert @lst[0].name.to_s.start_with?("tmp_")
     end
     def test_second_class
-      assert_equal Vool::LocalAssignment , @lst[1].class
+      assert_equal Sol::LocalAssignment , @lst[1].class
     end
     def test_second_name
       assert @lst[1].name.to_s.start_with?("tmp_")
     end
     def test_last_class
-      assert_equal Vool::IvarAssignment , @lst[2].class
+      assert_equal Sol::IvarAssignment , @lst[2].class
     end
     def test_second_name
       assert_equal :foo,  @lst[2].name