- remove superfluous implementations doing almost the same
- introduce pre/post traversal and transformers as foreach/map/fold
- Redefine other operations exists, contains, as folds
- Fix freshenLocals bug found by Ravi

- Simplify code generation by replacing CompilationEnvironment with a
  simple scope state.

- Support Choose construct in both evaluators.

- Introduce RecursiveEvaluator (renamed from Naive) and TracingEvaluator
  which tracks intermediate values as well.

- Introduce offset as well as ranged positions, extract all positions
  from trees. Try to propagate them as much as possible. Introduced
  .copiedFrom

- Remove dead-code, and improve TreeOps a bit.

- Introduce Pretty-printer arguments

small issues in the ChainProcessor system. Some tests ending in .BAK
should be runnable but can't for now because of a memory leak somewhere
in the framework.

Solvers wrap solvers or factories, depending on the needs.
Factories no longer wrap factories, except for the special case of
timeoutsolverfactories (it does it in a typesafe way though).

Fix TupleRewrite with new posts, fix ScopeSimplified, Fix pretty printer

- RewritingSolver
- DNFSolver
- UnrollingSolver