remove %pylab from pylab-switching
move pylab-switching to mpl-switching
pylab_figshow -> inline_figshow
remove pylab from desktop entrypoint and completion
remove pylab from internal_ipkernel example
remove pylab from the parallel examples
don't mention `--pylab` in R or cell magic notebooks
use mpl showcase instead of pylab examples

for %load
Merge pull request #5066 from minrk/pylab-examples

remove (almost) all mentions of pylab from our examples