Process each image completely before moving onto the next one

[dragos240]

Currently, the source fetching, tag fetching, and processing are done in for every file inside a stage before it moves onto the next stage, resulting in many calls at once to the same service, which can cause rate limiting. The application should, for each image, cycle through the whole process before the first stage is run again.

So instead of this:

• Lookup image source for img1... img2... imgN
• Lookup tags for source img1... img2... imgN

It should do this:

• Lookup image source for img1, lookup tags for source of img1
• Lookup image source for img2, lookup tags for source of img2