grid inside BorderContainer has various issues on IE

[bill]

See test_grid_layout_bordercontainer.html (tested on IE7).

1. Problems when Grid is direct child of BorderContainer instead of having intermediate ContentPane (modify demo/mail/demo.html to remove intermediate ContentPane to see this problem)

2. Doesn't work unless region=center is the last entry in the BorderContainer list (modify test_grid_layout_bordercontainer.html to see this problem)

3. top ContentPane just not showing up at all

[Nathan Toone]

(In [15360]) Fixes #7767 - actually set the height, like we promise to in the comment. !strict

[bill]

(In [15361]) refs #7767; splitter=true doesn't make sense on an height: auto pane

[bill]

(In [15362]) Remove intermediate ContentPane?; no longer needed. Fix width of table on IE. Refs #7767.