Updating the Lexer for filters
Adding the start of filtered projections
Adding the start of functions
More work on functions
Adding the ability to use multiple filters of a node and the ability to stack function calls
Moving functions out of the interpreter and adding the ability to register custom functions
Added validation rules to functions
Fixing validation error in function. Allowing functions at first token position.
Cleaning up debug output and showing broken stack info if needed
Adding more comments and fixing current node for functions in a projection
Restructuring how AT is added onto the stack
Adding the second operand to debug output
Removing some stack juggling in favor of tracking the current node for things like multi-select, or expressions, and filtering
Fixing null failure modes for functions
Added the ability to nest OR expressions in a filter expression
Added "is_falsey" opcode
Better syntax errors for bracket expressions
Removing unused opcodes
Removing currentToken and previousToken tracking
Cleaning up compile method
Trimming up a few lines
Adding interpreter tests