New text align class, .text-nowrap, for preventing text from breaking to new lines. Applies it to the grid docs table.

Fixes #13548: Use position: absolute; to fix checkbox and radio line-height problems that were introduced after #13003

Doing this the right way this time. Hiding .panel-footer top border when
preceeded by a .list-group. This should resolve the "double border"
issue.

Fixes #13066: Add z-index to the form control feedback icons so input groups don't render on top of them