Added trust_xheaders config option to delegate it to HTTPServer.

This is neccesary if the notebook app is proxied behind a reverse
proxy that handles SSL.
make qtconsole size at startup configurable
more precise help in config
adding stream kwarg to current.new_output

This was missing, and made unnecessarily clunky to create output cells
of stream type using the nbformat API.

Before this commit, you had to do something like

  from IPython.nbformat import current as c
  output = c.new_output('stream', the_text)
  output['stream'] = 'stdout'

after this commit

  from IPython.nbformat import current as c
  output = c.new_output('stream', the_text, stream='stdout')
Merge pull request #3041 from minrk/requirepush

support non-modules in @require
Merge pull request #3058 from minrk/redirect

add redirect handler for notebooks by name
Merge pull request #2981 from minrk/format_types

IPEP 10: kernel side filtering of display formats
Merge pull request #3162 from ivanov/output-stream-kwarg

adding stream kwarg to current.new_output

This was missing, and made unnecessarily clunky to create output cells
of stream type using the nbformat API.

Before this commit, you had to do something like

    from IPython.nbformat import current as c
    output = c.new_output('stream', the_text)
    output['stream'] = 'stdout'

after this commit

    from IPython.nbformat import current as c
    output = c.new_output('stream', the_text, stream='stdout')

and actually, that stream= argument defaults to 'stdout' if it isn't given.

I modified a test that will break if this functionality is ever removed.
Merge pull request #3152 from Carreau/qtconsole-config-size

make qtconsole size at startup configurable

use `(c.|--)IPythonWidget.(height|width)=<value>` to change the startup value.
Merge pull request #3147 from meteogrid/rproxy_support

Notebook support for a reverse proxy which handles SSL

Added a "trust_xheaders" config option to NotebookApp to enable the passing of the xheaders flag to tornado.HTTPServer. This is necessary so tornado can generate the correct wss:// scheme
raise UnsupportedOperation on iostream.fileno()

closes #3017