Improve replace filter

[davidmegginson]

1. Stop after first successful replacement (optionally continue?)
2. Optionally allow a default value if all replacements fail

[davidmegginson]

The filter is now optimised to recompile matching indices, and will stop after the first successful match for each cell. These changes should speed it up considerably for long maps.

[davidmegginson]

This change also makes it possible to add a default value to maps, using a regex at the end