Filters fixes

[lauxley]

• Stop lowering case of strings before filtering
• Stop pushing a mapping for every field if not needed/wanted
• fix some filtering chains syntaxes

[nasief]

@lauxley I had the same issue with the lower case on the values while filtering. When do u expect to merge this PR?

[lauxley]

Probably as soon as i start working again on this package, which is totally indefinite.