Fix nested ands ors

[michael-dean-haynie]

The IBM-style filter and() and or() operators should be nestable. This works for the @bitovi/sequelize-querystring-parser package but not for the @bitovi/objection-querystring-parser package.

Steps to Reproduce

1. Run the objection example
2. Use postman or curl to make a request with a querystring like this:

   
   // formatted readable version
   filter=or(
   equals(id,'1'),
   and(
       equals(id,'2'),
       greaterThan(id,'0')
   )
   )

// inline version filter=or(equals(id,‘1’),and(equals(id,‘2’),greaterThan(id,‘0’)))

3. The obj lib returns the following:
``` json
{
    "results": [
      {
        "fx": "where",
        "parameters": [
          "id",
          "=",
          1
        ]
      },
      {
        "fx": "where",
        "parameters": [
          "id",
          "=",
          2
        ]
      },
      {
        "fx": "where",
        "parameters": [
          "id",
          ">",
          0
        ]
      }
    ]
}

4. Notice that the result is a flat array without any of the nesting logic preserved.

Acceptance Criteria

• The filter logic for the @bitovi/objection-querystring-parser should support arbitrarily deeply nested sub-expressions using and() and or() operators.
• Once resolved, we should remove any disclaimers about this bug from the @bitovi/objection-querystring-parser readme.

NOTE: #29 is dependent on this nesting logic working because the not() operator uses a nested sub-expression.