Replaced "Error" by specific name of error considered and added other information when verbose=True.
Should be useful for debugging more quickly.
All verbose are now boolean too (some were int).
I changed the logging for the Zoom linesearch to partially fix the issue #555 (that is avoid printing errors when not required).
Previous comments (two levels printing, full wording) have also been tackled.
Replaced "Error" by specific name of error considered and added other information when verbose=True. Should be useful for debugging more quickly. All verbose are now boolean too (some were int).