Enhancing EQL Parser

Incoming changes description:

1. EntityQueryLanguage : Parses DSL strings like AIRCRAFT() .
2. Handling Multiple Argument : If an entity type (e.g., AIRCRAFT) can take multiple sub‐entities of the same kind (e.g., multiple AIRLINE(...) clauses), we accumulate them into a Python list internally.
3. Merging __matches__
   • In earlier code, merging two __matches__ dictionaries used +=, which failed (since you cannot += two dicts).
   • Now I suggestdict.update() and, when the same argument name appears twice, we convert the existing value into a list and append the new one.

Examples

1. How many aircrafts in the database. Expected dsl should be only AIRCRAFT()
2. How many aircrafts for Air France and Brussel Airlines. Expected dsl should be only AIRCRAFT(AIRLINE("Air France"), AIRLINE("Brussels airlines"))