Lab1.
Not a good lexer.
A simple Lexer is compeleted.
Parser is completed.
Add column number.
Add some error type.
Merge remote-tracking branch 'origin/Lab1' into Lab2

Conflicts:
	src/control/Control.java
AST is finished.
Finish a simple elaborator.
Merge remote-tracking branch 'origin/Lab2' into Lab3

Conflicts:
	src/control/Control.java