Programmatic SymbolicExpression construction API

[dabico]

It seems to me that there is no Java library for programmatically constructing S-Expressions. Within the context of this project, it would be used to ensure proper Query construction on the client end. And who knows, if it's useful enough on it's own it could evolve into a separate library.

Here's the official tree-sitter-query grammar definition that this API should be based on.