Add feature filter attribute

[FilipLeitner]

Add property to store a structured filter that specifies conditions for querying features based on their attributes.

Would be used for WFS and possibly ArcGIS (layers)

Values of the attribute would be JSON-like format to represent logical conditions originating in https://github.com/geostyler.
Example of property to value comaprison (or more here ):

[
    "&&",
    [
        "==",
        "status",
        "continuouslyWorking"
    ],
    [
        "||",
        [
            ">",
            "drilled",
            1950
        ],
        [
            "<",
            "drilled",
            2016
        ]
    ]
]

in case of property to property comparison geostyler function is used

[
  '<',
  {
    name: 'property',
    args: ['drilled'],
  },
  {
    name: 'property',
    args: ['discontinued'],
  },
];