Check for non-https resources

[davegaeddert]

There shouldn't be much of a need for scripts/styles/images/etc. that aren't https. So we should be able to make a check against it, and might need to finally add some sort of "check exception system" to ignore specific things where you have no other choice? With a hash of some sort.

Main point is to help avoid mixed content warnings.

[davegaeddert]

Part of sitechecks.