WIP/ENH: pyplot internals

In part addresses #903
probably more examples need to be updated.
This also addresses the matplotlib issues with Anaconda (should now work without self compiled matplotlib) reported in #728 by @kambysese.
We're now able to understand the reasons and extract two insigths:

1) don't mix plt.axes with plt.subplots
2) axes.figure | axes.get_figure and plt.gcf() are not the same. Really make sure get the right figure when doing multi-axis plots where multiple calls of ave.plot are made to draw on the same figure.

In addition many inconveniences can be avoided by explicitly invoking %pylab inline in a notebook. 
This should be added to the docs.

You can checkout this notebook for exploring:

http://nbviewer.ipython.org/7533330

The multi-axis figures now work in the notebook.
The block thing still needs a fix.