Refactor and simplify code in AspectClique. Write tests.

Treat a language and its sidekick (if any) as a single vertex.
Add all extended languages to the pool before building the graph.
Drop dubious invariant check.
Fix the second pass in findAspectCliques ingnoring the fact
that there might be leafs without aspects.

coderules/solutions/jetbrains.mps.coderules.test/jetbrains.mps.coderules.test.msd

@@ -20,6 +20,7 @@
     <dependency reexport="true">707c4fde-f79a-44b5-b3d7-b5cef8844ccf(jetbrains.mps.lang.test.runtime)</dependency>
     <dependency reexport="false">6998f568-f0e9-473b-b4a8-9efb6499fc8d(jetbrains.mps.coderules.typechecking)</dependency>
     <dependency reexport="false">f97d84b2-8bad-4fdd-8ede-da17b3eacf4c(jetbrains.mps.coderules)</dependency>
+    <dependency reexport="true">ff6372a2-2f45-4ec3-952b-02581666015f(jetbrains.mps.lang.coderules.template)</dependency>
   </dependencies>
   <languageVersions>
     <language slang="l:f3061a53-9226-4cc5-a443-f952ceaf5816:jetbrains.mps.baseLanguage" version="9" />