count_error_rows: Allow input to be specified as last arg(s) in addition to as stdin

exc.py: ExPercentTracker: When diplaying fraction of iters that had errors, don't duplicate the iter_text ("row", etc.) in the numerator

bin/map: Use new ExPercentTracker iter_num tracking to track distinct row #s with errors

exc.py: ExPercentTracker: Track iter_nums of Exceptions as well, to distinguish how many distinct iters had errors

Added bin/count_error_rows to count distinct rows with errors in `map` error messages

input.Makefile: Changed "%.out: .make" rule to ": %.make" so that any file can be built from a corresponding .make file. This will allow flat files to be retrieved dynamically by running an associated .make file.

xml_func.py: FormatException: Inherit from ExceptionWithCause instead of SyntaxError because a FormatException signals a different kind of error condition (related to the input value rather than the function syntax)

xml_func.py: Renamed SyntaxException to SyntaxError because it's a user error signaling invalid mappings syntax

xml_func.py: SyntaxException: Use ExceptionWithCause to combine msg and cause's msg because it now combines them on one line, which is needed for bin/error_stats to work properly

exc.py: ExceptionWithCause: Prepend msg to cause's msg separated by ': ' instead of '\ncause: '