This eases proofs, because lists computes. It also avoids issues with duplicates (so, no
more environment splitting judgment, just append).

commit e0d15199
Author: jihgfee <jihgfee@gmail.com>
Date:   Wed Sep 16 14:20:00 2020 +0200

    Refactoring - Moved spar to own file and renamed as par_start

commit fd7dc61d
Author: jihgfee <jihgfee@gmail.com>
Date:   Wed Sep 16 13:10:42 2020 +0200

    Proved spar using typing rule instead of breaking abstraction

commit 821a4c23
Author: jihgfee <jihgfee@gmail.com>
Date:   Tue Sep 15 17:11:20 2020 +0200

    Whitespace cleanup

commit eb01938a
Author: jihgfee <jihgfee@gmail.com>
Date:   Tue Sep 15 17:10:37 2020 +0200

    Added a parallel composition for lambdas over channels