[Expression Tree][New/Refactor] Refactored to new ExpressionTreePtr syntax. Added Block and File trees.
[Token][New]Added if, then, else token types.
[Parser][Refactor]Refactored Parser to be more modular. Added support for files with multiple statements.
[Tokenizer][Refactor]Refactored the tokenizer and added if/then/else tokens.
[Parser][Bugfix]Parser now works. Tweaked the modularity. Added Comments.