Major changes:

- Global ttab object is now thread-safe
- All related descriptions are now static
- Add OBTranslator object for translating operations

Minor changes:

- Remove unused variables
- Address some memory-related issues

TODO:

- member variable names are not consistent
- PatternFP descriptions are not the same as before

This resolves openbabel#2269.

Major Changes:

- Add OBResidueObserver class for residue operations
- Change global static mutexes into protected class member variables
- Add OBGlobalDBMutex class to address copyability issue

- OBMol, OBBase, and OBError classes are partially thread-safe
- Fix a static function-local variable in OBConversion to thread_local static variable