#147 add progress bar to help make JML tools a better backend

[Joseph Kiniry]

In a recent discussion with Werner Dietl about ETHZ's JML2 plugin, the following idea popped up:

Joe said:
> - Adding a progress bar to the aforementioned
> modal indow would be useful.

To which Werner responded:
>> I do not get any feedback from the JML2 compiler,
>> so all I can say is "in progress".

To which Joe finally responded:
True. Perhaps we should add a switch to the JML tool suite so that they are more useful as backends? E.g., something that would print an ASCII progress bar that front-ends, including humans, could interpret. I'll add a tracker item for this idea now.

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Proposal: Add a --progressBar/-pb switch which, when activated, prints a progress bar to either STDOUT or STDERR (wherever our warnings/errors do not go).

The bar might, e.g., look like this:
[********=============================]
and the fill ratio might relate to the number of classes typechecked/compiled/etc. thus far compared to how many must be processed in the given run.