Added support for passing command line arguments

[EliasC]

The main method in Main may now have a single argument of type
[string]. This array contains the strings of argv that were passed
to the underlying C-program. Note that there is no need to pass argc
since encore arrays store their length. main may still have an empty
argument list.

Here is an example program that prints its argument list:

class Main
  def main(argv : [string]) : void
    repeat i <- |argv|
      print argv[i]

[albertnetymk]

Trailing space is introduced in a few places. Other than that, I feel this PR is OK.

[EliasC]

Trailing space removed.