Addition on SIS web site

[Martin Desruisseaux]

Hello all

I just added a first draft of a page about the command-line interface on 
the SIS web site [1]. I also opportunistically added some note and links 
about MathML usage in source code [2].

    Martin

[1] http://sis.apache.org/command-line.html
[2] http://sis.apache.org/source.html#mathml