Move test code from ESS

[vspinu]

[lionel-]

This probably should be the first step before any refactoring in indentation/syntax code.

One thing that's lacking in the test framework is regeneration of literate test cases in temporary files to check that nothing changed (just like you implemented for indent cases). Currently it just regenerates the test cases which is not good since launching tests won't notify failures. The failed cases will just show up in git diff and could go unnoticed in a git commit.