Automatically switch to another project if unable to get an item from the tracker

[JesseWeinstein]

It would be nice if, when the Archiveteam's Choice project is selected, and the actual project is rate limited such that items aren't available, the Warrior would automatically fallback to another project, rather than just waiting.

I may try to code this up myself, especially if others think it is a good idea.

[chfoo]

Related: #50, #36, #84

[ConstantineK]

I also was thinking that if the requests were distributed among all projects (in some new mode) it would be less likely to get rate limited as you would be distributing your reads across the nodes to the different sites even more.