Refactor filter parsing in JS code

[PhilippWendler]

In the HTML tables, filter state is stored (like other state) in URLs and thus serialized in string form. It seems that deserialization and parsing occurs more often than necessary and with duplicated code, which is highly error-prone. For example, the code .split("_") for separating a filter id into pieces occurs already four times (in ReactTable.js, utils.js, FilterBox.js, and filters.js), and #730 is adding more cases.

This should be refactored such that there is no code duplication and ideally each string is used only once and converted into a proper object-oriented representation, and the latter is used by the rest of the code.