Replace random_integers with randint

Fix a 'DeprecationWarning: Passing 1d arrays as data is deprecated in
0.17 and will raise ValueError in 0.19. Reshape your data either using
X.reshape(-1, 1) if your data has a single feature or X.reshape(1, -1)
if it contains a single sample.' from scikit-learn

Fix a 'VisibleDeprecationWarning: using a non-integer number instead of
an integer will result in an error in the future'

Fix FutureDeprecationWarnings due to PEP 479

A OWWidget can be constructed only with only a mainArea (no controlArea,
e.g. 'OWDistanceMatrix') in which case the constant index was incorect.

Fixes a warning 'QSplitter::setCollapsible: Index 1 out of range' from
Qt

Suppress a "FutureWarning: in the future, full(...) will return an
array of dtype('int64')"

Was broken since 2329179

Suppress a 'DeprecationWarning: numpy boolean subtract, the `-` operator,
is deprecated, use the bitwise_xor, the `^` operator, or the logical_xor
function instead'

Suppress a warning from Qt ('QGraphicsScene::addItem: item has already
been added to this scene')

In numpy 1.12b passing the distribution.Continuous instance as the
weight parameter to np.average triggers a:

    File "..numpy/lib/function_base.py", line 1138, in average
        if (scl == 0.0).any():
    AttributeError: 'bool' object has no attribute 'any'

Passing a ndarray subclass to numpy.average triggers a:

    FutureWarning: np.average currently does not preserve subclasses, but
    will do so in the future to match the behavior of most other numpy
    functions such as np.mean. In particular, this means calls which
    returned a scalar may return a 0-d subclass object instead.

In this case this is not what we want.

Compute a 'weighted count' of NaNs if weights vector is supplied