Add ability to ignore all errors on run

[bethac07]

In CellProfiler/CellProfiler#4486 and CellProfiler/CellProfiler#4527, as well as at other times, people have asked for ways to just skip one or two bad images. For the reasons laid out in the new ALWAYS_CONTINUE_HELP, that is going to sometimes be a bad idea because it will just kick the can of failure down the road to make you fail later, but for some workflows it's undeniably helpful. Note that this PR only introduces the settings, the companion PR in the main repo will be the only way to actually set them.

ALWAYS_CONTINUE_HELP = """\
Determines whether CellProfiler should always skip images that 
cause errors to be raised vs stopping analysis (in headless mode)
or asking the user what to do (in GUI mode). This may help in 
processing large image sets with a small number of unusual or corrupted
images, but note that the skip of the original image set in question 
may cause issues with modules that look atmultiple image sets across 
groups (CorrectIlluminationCalculate, TrackObjects) or in Export modules,
leading to simply a later failure. Use at your own risk.
"""