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

lib/ruby/statement.rb

@@ -7,16 +7,16 @@ module Ruby
   #
   class Statement
 
-    # Many statements exist in the vool layer in quite a similar arrangement
+    # Many statements exist in the sol layer in quite a similar arrangement
     # Especially for different types of assignment we can abstract the creation
-    # of the vool, by using the right class to instantiate, the "vool_brother"
-    # Ie same class_name, but in the Vool module
-    def vool_brother
-      eval "Vool::#{class_name}"
+    # of the sol, by using the right class to instantiate, the "sol_brother"
+    # Ie same class_name, but in the Sol module
+    def sol_brother
+      eval "Sol::#{class_name}"
     end
 
     # return the class name without the module
-    # used to evaluate the vool_brother
+    # used to evaluate the sol_brother
     def class_name
       self.class.name.split("::").last
     end