Fix serialization bug introduced with refactored code

Introduced with 717abc05917814f143c0a7789ba1534c70716235
Refactor, cleanup and add documentation.

- add Default instances
- default FuzzyConfig uses english replacements instead of german now
- ProcessConfig does not optimize query by default anymore
  (unnecessary)
- newtype for CompressedOccurrences in Simple9
- rename functions
  - execCmd -> execBasicCmd
  - execCommand -> execCmd
- cleanup exports
- cleanup ContextIndex (incomplete)
  - add 'deleteContext' for ContextIndex
    and rename 'deleteContext' on ContextMap to 'deleteContext''
  - use ContextMap smart constructor consistently