Simplify AST, replace node per operator with just ComparisonNode (WIP)
Simplify support for custom operators, no need for RSQLNodesFactory
Rename LogicalOp to LogicalOperator

Just to be consistent in naming…
Rename RSQLNodesFactory to NodesFactory
Validate that no multiple arguments given for single-value operator
Validate symbol(s) given in ComparisonOperator
Update JavaDoc
Remove unused method
Add test for accept() in nodes
Update readme