respect `pylab_import_all` when `--pylab` specified at the command-line

Earlier cleanup cleaned up a bit too much, ignoring this configurable.

should be backported to 1.x
Drop monkeypatch for pre-1.0 nose

Closes gh-484
rename post_processors submodule to postprocessors
Also renamed local variables in nbconvertapp
Use msvcrt.getwch() for Windows pager.

Closes gh-1591
Merge pull request #1 from jdfreder/rename_postprocessors

Also renamed local variables in nbconvertapp
Merge pull request #4073 from jakevdp/rename_postprocessors

rename ``post_processors`` submodule to ``postprocessors``
Merge pull request #4084 from takluyver/win-page-py3

Use msvcrt.getwch() for Windows pager.
fix missing import
Merge pull request #4086 from ivanov/missing-errno

fix missing errno import
Make Qt console banner configurable
Merge pull request #4091 from takluyver/qt-banner-config

Make Qt console banner configurable
Merge pull request #4056 from minrk/pylab_import_all

respect `pylab_import_all` when `--pylab` specified at the command-line
Update target branch before backporting PR
Merge pull request #4069 from takluyver/drop-nosepatch

Drop monkeypatch for pre-1.0 nose
Merge pull request #4094 from takluyver/backport-pull-target

Update target branch before backporting PR