Deprecate detection of IPython frontends
The check for the Qt console won't be necessary in IPython 3 and above: we decided that the Qt console's display of HTML reprs was so bad that it shouldn't attempt to show them. We also want to remove the `parent_appname` config value (ipython/ipython#4980), which will break both of these functions (making them always return False).

The assignment to `ipnbh` was redundant - nothing used that variable. I guess it was used previously and didn't get cleaned up during some changes (quite possibly my own omission).

About the qtconsole, then this issue #7372 can maybe closed? (which is a nice illustration of how bad it can be ...)
 I've rebased this pull request - I think it's ready for review.
 is their a min ipython version that this requires? (we don't test this per se), e.g. will this break with an older version of ipython but pandas 0.14.1/master? 
 I've not actually changed anything functionally (the assignment I removed is an unused variable), so no, it won't break.

When IPython 3.0 has been out for a while, I'll make another PR to remove this code. This deprecation is just to ensure pandas doesn't start using this functionality for anything new while we're removing it.
 so if someone uses ipython 0.11 it will still work the same?
 Yes - this PR should not change how anything actually works whatsoever. All it does is:
- Add deprecation notes in comments and docstrings
- Remove an assignment to an unused variable
 thanks!
