Extension to match two objects, using partial equality.

For example, an object with the following properties:

{
"A": 123,
"B": "some value"
"C":[ 100, 200, 300]
}

Will match the following objects, because any non-default values are equal:

{   "A": 123  } or  {   "B": "some value"  } or { "C":[ 100, 200, 300] }

Whereas it will NOT match these objects, because they have fields that don't match:

{   "A": 456  } or  {   "B": "some other value"  } or { "C":[ 100, 200, 300, 400] } or { D: 123 }

This code is very useful in Testing, where we want to compare an actual and an expected result, but only on some attributes, not all.