ENH/CLN: add helpers for ipnb detection
ENH: special case HTML repr behaviour on ipnb GH3573

PTF
ENH: disable qtconsole HTML output again. add explanation why.
DOC: update RELEASE.rst
BUG: rework display logic again. deprecate display.height
DOC: Update Faq section on repr display options
DOC: update RELEASE.rst

PTF
Merge PR #3663