Add support for prefetching fields This makes it possible to specify the fields that should be prefetched as part of a getForFields query. Doing a prefetch on a ReferenceProperty when it is known that the property will be referenced in (almost all) entities is far more efficient than doing the invididual fetches sequentially.

"""
Code used in a couple of places to work with the current thread's environment.
Current users include i18n and request prefix handling.
"""

try:
    import threading
    currentThread = threading.currentThread
except ImportError:
    def currentThread():
        return "no threading"