add option to not stop after finding violation

[Stephen Siegel]

If the verifier can't prove an array index is in bounds, it could report the possible violation, save the trace, and then add the assumption that the index is in bounds and continue the search. Ditto for other classes of errors. This would allow the tool to find many errors at once.

[ywei]

We should also limit the amount of warnings to one warning per line of code/statement to prevent same warnings from being reported.

[Stephen Siegel]

Done. New commandline option -errorBound=N can be used to specify upper bound on number of errors found. Errors are categorized into equivalence classes and only one from each class is held.