Python bindings export `sum` which returns 4-tuples (Bug #902)

The sum function exported by python bindings returns unexpected results which are not documented. Potential conflicts with the code which uses numpy/scipy.

cv.sum returns 4-tuples, where the first item is the sum of the numpy array, and the remaining three seem to be zeros (I didn't observe other values).

Example (from ipython shell):

import numpy, cv; x=numpy.arange(10) ; sum(x) ; numpy.sum(x) ; cv.sum(x)

45
45
(45.0, 0.0, 0.0, 0.0)

numpy.+version+ ; cv.+version+ ;

'1.5.0'
'$Rev: 3057 $'

!uname -srom

Linux 2.6.34-020634-generic x86_64 GNU/Linux

cv.sum.+doc+

'sum(src) -> retval'

This is confusing, because

1. existance of cv.sum is not document and it doesn't 
     follow the naming conventions of [[OpenCV]], so the user
     doesn't expect that if sum suddenly works wrong,
     it is [[OpenCV]] import which may be responsible;
  2. this behavior is inconsistent with the behavior of numpy's
     and builtin sum@s and breaks a lot of code;
  3. this result of @cv.sum is not documented; the docstring
     of cv.sum tells only: "sum(src) -> retval". The semantics
     of the returned tuple is not explained.

This is also a reason why from cv import * cannot be used even in small quick and dirty scripts which happen to use also numpy or scipy. Other forms (import cv; from cv import Foo, Bar, Baz, ...) require a lot of additional typing (redundant cv. prefix to all constansts, like cv.CV_32F, and function names, or very long explicit import lists).

Other potentially problematic functions in cv module, which share common names with numpy functions, are: add, bitwise_and, bitwise_not, bitwise_or, bitwise_xor, divide, exp, invert, log, max, mean, min, multiply, repeat, resize, sort, split, sqrt, subtract, sum, trace, transpose

I suggest

• either do not export these lower-case functions from cv
• or document their behavior and move them in a separate package
• or make them compatible with numpy functions