Support persistent URL for plots

[rogerdahl]

From Sarah Elmendorf:

Last, and this might be well outside what the software can accommodate, is it possible to make a persistent url for a particular way of plotting a particular dataset? Thinking here of non-academic end users who are interested in viewing our data but not interested in learning how to find data on EDI, select by dataset ID, choose the right tab and plot. For example someone we work with that JUST wants to each year visualize the nitrogen trends at a particular site. If I could set up the plot as they want it and then just email them the link to visualize it (or put the url on our website), this would probably get them to look at it in a way that sending a n-step instructions of “go to the edirpository.org, scroll down to the 2nd table and click the dex button, then select this value for y, this one for y, check the box for make lines, etc” would be just too much legwork/too many steps.