Add documentation for Alliance of Genome Resources Pathway Viewer

[pgaudet]

On the Tools overview page:
http://geneontology.org/docs/tools-overview/

Added this text and image:

Summaries of GO-CAM Models are viewable on the Alliance of Genome Resources webpages for relevant genes. The Alliance of Genome Resources Pathway Viewer is designed to easily visualize the pathways in which a gene product play a role, and to give eaasy access to the functions of the other genes in the same pathway, listed in a menu on the right (see example below).

The Alliance of Genome Resources Pathway Viewer is integrated in the Alliance of Genome Resources{:target="blank"} and work is underway for further integration in several projects. Alliance of Genome Resources pages display models containing a minimum of 3 connected molecular functions (a.k.a. Activity Units).

Based on information provided in geneontology/noctua#757 (comment)

@vanaukenk please let me know if you have suggestions for improvement
@kltm Could we add more information like we have for the Ribbon doc?

Interested to learn more about the GO Ribbon ? Check the GO Ribbon documentation

Want to try it now with your genes ? [ Access the GO Ribbon sandbox ]

Whhere would these link?