Extra filter types

[samgranger]

It would be nice to see the following types of filters:

• Numeric range, so if you have a column with numeric values, users can specify a number between x and y.
• Multiselect, so users can filter where column value equals x or y.

[rappasoft]

I don't know if I have time this month to do it, but you can always submit a PR and I'll merge or build on it. You could use this one as a reference: #332

Right now I don't have any support for side-by-side filters which I've been meaning to add. Which would probably be needed for a range from a UI perspective. Right now my "from - to" date ranges in my apps are just on top of each other.

[AlexHaible]

Adding to this: A simple string filter would also be great to have.