Enhancement: Improve filters programming interface

Problem

Right now filters are passed to BaseResource.find as an object and are parsed inside every adapter separately.

• Passing object is ugly because we have to create it on AdminBro core and pass to the adapter
• Current filter structure doesn't allow to filter by let say greater than in integers, or by relation.

We have to change Filter instance to a simple filter object with the strict interface.

Interface proposal (example)

type FilterQuery = {
    eq?: string,
    gt?: string,
    lt?: string,
    contain?: string, // for like
    in?: Array<string>
  }

type Filter = {
  [path: string]: FilterQuery | Array<FilterQuery> | {and: Array<FilterQuery>}
}

Array would be for "or"

Acceptance criteria

In this task:

• unify the filters programming interface
• the best would be if it will be backwards compatible
• allow adapters to define which operations they support. Mybe some new adapter couldn't support in?
• it should be possible to filter by nested properties

Possibilities after this change

• we will be able to add filter to ResourceOptions which will restrict the list/search actions - or to list Action interface.
• we could pass filter in useRecords hook
• we could pass filter in PropertyOptions of the property responsible for handing one to many relationshipp