Add error_document to OperationFailure PYTHON-576

This change adds an error_document attribute to
OperationFailure and subclasses. The error_document
attr will be the complete error document returned by
the server, when available. The error document may
include valuable information other than just the error
message, particularly when connected to mongos, which
may return one or more error subdocuments representing
errors on multiple shards.

Extend insert(), update(), save() and remove() functionality:

insert(), save(): add full_response argument by analogy with find_and_modify()
insert(), update(), save(), remove(): add wtimeout_is_error argument

BUMP 2.6.3

BUMP 2.6.2

BUMP 2.6.1

BUMP 2.6

BUMP 2.5.2

BUMP 2.5.1

BUMP 2.5

BUMP 2.4.2