Constants, expression parser, optimizer, bytecode

- Small changes to constants
- New message for wrong parameter's type when calling functions
- New message for wrong type in assignments
- Added optimizations for 1-argument opcodes
- Added type check for operators: `+=`, `-=`, `*=` (...)
- Added global constants
- Fixed the `=` operator in code like: println(variable = 10);
- Fixed saving bytecode
- Fixed optimizer on fjmp/tjmp
- Fixed `do..while` loop
- Fixed `,` syntax checking
- Changed bytecode strings saving