Fix and improve log output at different verbosity levels

[antond-weta]

Currently the log output looks a bit inconsistent.

We need to ensure that the tool prints out the relevant information in all modes, increasing with each verbosity level.

[aabhinavvvvvvv]

Hi @antond-weta, I've fixed the inconsistencies in curveFit() (Ceres report was on stdout while everything else used stderr, BriefReport was printing at level 1 when it shouldn't).

For the broader redesign, I'd like your input on the intended level scheme before touching more code. Currently at -v (level 1) we already get WB coefficients, IDT matrix values, and cache hit/miss messages — which maybe a lot. Would you prefer something like:

• Level 1 (-v): Steps only ("Loading image", "Saving output", "Found illuminant")
• Level 2 (-v -v): + WB coefficients, IDT matrix, Ceres full report
• Level 3 (-v -v -v): + Cache internals, minimizer progress

This would require updating some existing tests in testColourTransforms.cpp that currently assert those messages appear at level 1.

[antond-weta]

@aabhinavvvvvvv that looks good, thanks!

Perhaps move the ceres report to level 3, and the minimiser progress to level 4?

We should also take a look at the warnings. Some are being always shown, but others only in verbose modes.

[aabhinavvvvvvv]

I've addressed all the points in PR #249