All-seeing synthesis with Oracles, library reorganisation

- NormalizationRule becomes priorities, so that we can have multiple
  distinct layers

- Use the @library annotation, move synthesis stuff to synthesis,
  Oracles.

- Make sure tests use PreprocessingPhase and import synthesis when
  adequate

- Extract proper package objects fix patternRecons and simplifiers

- Reorganize library:
  - leon.{choose,???} -> leon.lang.synthesis
  - leon.{waypoint,epsilon} -> leon.lang.xlang