Add countere of files read, files needing updates, files skipped etc

[hazendaz]

Many plugins give insight into what exactly they are doing even if its nothing. It would be a nice improvement to start adding counters which would help with #904 in showing the true issue there.

Today this plugin can be rather verbose which is unnecessary under normal run as it simply lists all the files that were updated. That logic can remain but should be debug mode to help make it easier to read out general output. Git or whatever SCM used is going to show that info anyways.

Something like this would be useful.

[INFO] --- impsort:1.12.0:sort (default) @ base-parent ---
[INFO] Processed 0 files in 00:00.000 (Already Sorted: 0, Needed Sorting: 0)

[hazendaz]

note: my example was from a parent pom, of course it has nothing to sort, it had no source. But the idea is that it very clearly states how many files processed, some time it took, those that needed it and those that did not.