Ignore line numbers in dialyzer ignore file

This change uses sed to remove the line numbers from the ignore file and
the warnings file. That way the comparison doesn't care if line numbers
change, which happens very often.

Notice that the final output does not have the current line number for
the warning. I think that is OK for now.  With some trickery involving
sort and sed the original line numbers could be re-added to the output,
but that will have to wait for another day.
Ignore ignore file numbers, but consider count

The bulk of the code deals with the dialyzer.ignore-warnings file
which contains strings to ignore if output by dialyzer.
Typically the strings include line numbers. Using them exactly is hard
to maintain as the code changes. This approach instead ignores the line
numbers, but takes into account the number of times a string is listed
for a given file (See the sort + uniq -c commands, which add the count
as a prefix). So if one string is listed once, for example, and it
appears twice in the warnings for that file, the user is alerted.
It is possible but unlikely that this approach could mask a warning if one
ignored warning is removed and two warnings of the same kind appear in the
file, for example. But it is a trade-off that seems worth it.