Add flags to the program.

[tobias-wilfert]

Now that there is some functionality it makes sense to add flags to the program:

• A flag to indicate wether the AST representation should be outputted
• A flag to decide where the AST should be outputted (file or printed out)
• A flag to decide whether the generated code should be printed or outputted to a file
• A flag to decide if safe or readable code should be generated.