Removed the unused Syntax.Expected class hierarchy. The definitions module contains classes used to represent operands. Changed the Opcode's parsing algorithm to create a template that describes where operands are inserted into generated opcodes. Introduced a look-up dictionary in the Instruction class that is used to hold definitions of the arguments when parsed. Added a generate method to the Instruction class to perform operand substitution into the opcode template for each instance. Fixed the definition of the PUSH opcode.