matplotlib Code

The previous fix broke the current behaviour of being able to explicitly set a new unit type for a
specific axis after it was already set. This fixes that.

reverted bogus renderer dpi addition to text cache key

added the renderer dpi to the cache key for text

Fixed contour to now properly strip away units for unitized data on the x and y axes.
Unit registry now properly determines the registered converter to use for nested array data types.

reduce IDLE_DELAY to 5ms so mouse drags don't kill updates

Fixed bug #1889750.
Now an axes will not attempt to determine the default units to use if units have already been determined for a particular Axis.
Previously, by doing this it would override any axis labels set whenever any unit determination calls were made. This can still happen, but now some of the unneccessary unit determination calls are no longer being made.

cosmetic changes

2008-09-14 Reorganized cbook and mlab methods related to numerical
calculations that have little to do with the goals of those two
modules into a separate module numerical_methods.py
Also, added ability to select points and stop point selection
with keyboard in ginput and manual contour labeling code.
Finally, fixed contour labeling bug. - DMK

* Moved several function in mlab.py and cbook.py into a separate module
numerical_methods.py because they were unrelated to the initial purpose of
mlab or cbook and appeared more coherent elsewhere.

moved font examples to api

added a couple of font examples