Rebin parameters don't all apply to InterpolatingRebin

Also amalgamates code to accept single bin width as input rebin parameter.
Refs #9574
Usage example for InterpolatingRebin.

Also updated Rebin documentation to provide linkable content so that
InterpolatingRebin can refer to it.
Refs #9574
Centre out-of-line equations on their line.

The css that should do this in basic.css doesn't work with the bootstrap
theme as it has an extra div.body tag on the section containing
"text-align: center" so that it doesn't match in the bootstrap theme.
Refs #9574
Usage examples and doc cleanup for Polynomial correction.

Refs #9574