default graphs and other UI changes

[Hannah]

I think the mailing list is the place to announce new features, so I added in a function for generating default graphs and fixed the javascript and html so that there's only one graph at a time (which I realized probably works out as a better UI 'cause I end up requesting a graph multiple times when I don't see it generating 'cause it's below my screen) and the loading image actually works as it's supposed to.

So turning default graphs on/off can be controlled by uncommenting/commenting out the call to defaultGraph in loadDataOptions in https://code.google.com/p/ccp-viz-toolkit/source/browse/ccpweb/ccpweb/static/ccpweb.js

(and yes, this is documented in the code and wiki)