Documentation site needs flow charts

[djhoese]

I created some flow charts/block diagrams a while ago, but the general structure for polar2grid has changed and there is a lot more flexibility involved so I should redo these and include them in the documentation site. They will need to be relatively small so we don't hit the size limit for github (I'm not sure what that is anymore). I'm still not sure of whether or not I'll want to include the Omnigraffle project file in the repository.