filter_errors: Default to outputing only the first match

xpath.py: Added append() to recursively append subpath to every leaf of a path tree. parse(): Use append() to fix bug in split path parsing where subpath was not added to every leaf of the tree, only the main leaf of the main branch and the main leaves of the other branches of the last element.

exc.py: Changed to store multiple tracebacks in an exception, in case an exception is caught and re-raised inside an ExceptionWithCause wrapper. This preserves more of the traceback in this situation, because you get the ExceptionWithCause's traceback as well.

input.Makefile: import: Removed verbose=1 because verbose mode is now automatically on (except in test mode)

bin/map: verbose mode defaults to off in test mode and on otherwise

bin/map: In verbose mode, print which input rows will be processed

bin/map: n option: Defaults to 1 in test mode. Empty string "" is interpreted as None (previously n would have to be unset to specify None).

bin/map: Added section comments to env var config retrieval. Reordered env var config retrieval to put DB config last, since these options are input-type specific and complex, and putting them first hides the more general other options.

bin/map: Added section comments to env var config retrieval. Reordered env var config retrieval to put DB config last, since these options are input-type specific and complex, and putting them first hides the more general other options.

inputs/SALVIAS*/maps/VegX.plots.csv: Updated _units for % -> decimal conversion to use new syntax