Python for async:
- Various fixes to allow test_async01.py to work for string key/value.
- Hand rolled AsyncCallback class to mirror C's WT_ASYNC_CALLBACK.
- Keep the async callback in the PY_CALLBACK struct hidden in cursor's
  lang_private.
- Some cleanups in writeToPythonStream(), including fixing
  potential race condition.

Java for async:
- Modified Java SWIG interfaces for async enough to allow it compile.
- Standardized class spelling to 'AsyncOp'.
- Removed a few non-applicable methods from AsyncOp.
Python for async:
- Various fixes to allow test_async01.py to work for string key/value.
- Hand rolled AsyncCallback class to mirror C's WT_ASYNC_CALLBACK.
- Keep the async callback in the PY_CALLBACK struct hidden in cursor's
  lang_private.
- Some cleanups in writeToPythonStream(), including fixing
  potential race condition.

Java for async:
- Modified Java SWIG interfaces for async enough to allow it compile.
- Standardized class spelling to 'AsyncOp'.
- Removed a few non-applicable methods from AsyncOp.
Merge pull request #983 from wiredtiger/async-python

Async python