Add semantic-comparison logic for queries/expressions

[orlavy-bigabid]

I would like to test function that return 'squel' query/expr object so I think there should be a method to compare identity between 'squel' products. Somthing like this :

const exp1 = squel.expr().and('age = ?', 54).and('salary >', 10000);

const exp2 = squel.expr().and('age = ?', 54).and('salary >', 10000);

expr1.isEqual(exp2) // true