BUG: Fix DataProbe loading error when NumPy is not available

This commit allows "SliceAnnotations" to gracefully handle the case
when the application is built without NumPy support.

The error fixed by this commit is the following:

//--------------
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/home/jcfr/Projects/Slicer-Debug/Slicer-build/lib/Slicer-4.4/qt-scripted-modules/DataProbe.py", line 5, in <module>
import DataProbeLib
File "/home/jcfr/Projects/Slicer-Debug/Slicer-build/lib/Slicer-4.4/qt-scripted-modules/DataProbeLib/init.py", line 1, in <module>
from SliceViewAnnotations import *
File "/home/jcfr/Projects/Slicer-Debug/Slicer-build/lib/Slicer-4.4/qt-scripted-modules/DataProbeLib/SliceViewAnnotations.py", line 2, in <module>
import numpy as np
ImportError: No module named numpy
setPythonSource - Failed to execute file "/home/jcfr/Projects/Slicer-Debug/Slicer-build/lib/Slicer-4.4/qt-scripted-modules/DataProbe.py" !
Fail to instantiate module "DataProbe"
//--------------

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24089 3bd1e089-480b-0410-8dfb-8563597acbee