Fix specs so it will look for Browser.modernie

Added Browser.modernie to speccs browser check
Docs: Updated Browser docs.
Browser: Change Browser.modernie to be for <1.4compat> only.
Browser: Remove Browser.modernie completely, just delete Browser.ie for IE11+ in <1.4compat>.

Taking the most defensive "fix" for the IE11 problem, since the
discussion is still not resolved. Least change -> least problems.

If `modernie` is preferred anyway, someone can revert that back in
later.
Docs: Move Browser.Plugins.Flash to deprecated section.
Remove modernie from specs
Docs: Added section about Browser.ie vs. Browser.modernie.
merge: Revisiting modernie approach.
Merge pull request #2569 from timwienk/browser-ie11

Browser ie11