Redirect more logging through new log framework.

Remove all remaining uses of `console`.  Made a couple of modules
fit the standard "module.exports is a constructor" pattern, which
let us factor out redundant parameters from method calls (and
efficiently share loggers).

Change-Id: Ib959b5d648bba87b65c4fe71c607d57e545bbeb7
Easy-to-read filenames in the bundle when debugging.

Change-Id: I093c5bb404d65a083c2f0c804acca36076521546
Don't crash if a referenced image was deleted or otherwise missing.

Change-Id: I6cea40912b03162f47f4c71d4765be907011399b
Increase retries of truncated downloads from 3 to 5.

Change-Id: I84fa60aa608821d8404be3432a1ca861a4f4809d