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/sol/README.md

@@ -0,0 +1,36 @@
+# SOL
+
+Simple Object Language
+--------------------------------
+
+in other words, ruby without the fluff.
+
+Possibly later other languages can compile to this level and use rx-file as code definition.
+
+## Syntax tree
+
+Sol is a layer with concrete syntax tree, just like the ruby layer above.
+Sol is just simplified, without fluff, see below.
+
+The next layer down is the SlotMachine, which uses an instruction list.
+
+The nodes of the syntax tree are all the things one would expect from a language,
+if statements and the like. There is no context yet, and actual objects,
+representing classes and methods, will be created on the way down.
+
+## Fluff
+
+Ruby has lots of duplication to help programmers to write less. An obvious example is the
+existence of until, which really means if not. Other examples, some more impactful are:
+
+- No implicit blocks, those get passed as normal arguments (the last)
+- No splats
+- no case
+- no elseif (no unless, no ternary operator)
+- no global variables.
+
+## Parfait objects
+
+The compilation process ends up creating (parfait) objects to represent
+things like classes, types and constants. This is done in this layer,
+on the way down to SlotMachine (ie not during init)