swallow enter event in rename dialog

avoids adding newline in cell after dialog is closed.

closes #3926
Merge pull request #3929 from minrk/rename-cr

swallow enter event in rename dialog

avoids adding newline in cell after dialog is closed.

closes #3926
FIXED logic of verbose flag in PDF post processor
Merge pull request #3934 from jdfreder/backport_fixes2

nbconvert: fix logic of verbose flag in PDF post processor
FIXED, don't try to create an empty directory
Merge pull request #3943 from jdfreder/nbconvert_reveal_winfix

nbconvert: Serve post-processor Windows fix
use sphinx.package_dir to find texinputs

this can be different for debian installs, etc.
add `--interaction=batchmode` to pdflatex call

avoids waiting for input
Merge pull request #3948 from minrk/sphinx-dir

Sphinx and PDF tweaks for nbconvert:

- add `--interaction=batchmode` to pdflatex call to avoid waiting for interactive input.

- use sphinx.package_dir to find texinputs directory regardless of on-disk location.

Closes #3894.
recompile css