The basic "map" function supported to clean up errors in data from
input sources is currently restricted to replacing the complete output
values. This is inflexible and requires specific entries for every output
value that require modification.

This update adds two new correction functions to mapfilters.cfg 

1. replace
This function allows setting up a proper substring replacement. The
replacement value is still restricted to a "literal", but only the matched
string will be replaced, not the entire data field.

This function also allows substring deletion (by leaving the second 
parameter empty)

2. extract
This function allows extracting one substring from a data field for
output

Detailed documentation for this functionallity can be found in
the included sample configuration file provided in the patch
(mapfilters.cfg.new).