[dfmc-modeling] Remove method environment(<&method>).

This method wasn't used and returned an empty vector rather than
a valid environment object.
[dfmc-modeling] Tighten types on environment generic & methods.
Remove unused local bindings.
Merge pull request #781 from waywardmonkeys/method-environment

Method environment
Merge pull request #790 from fracek/remove-unused-local-bindings

Remove unused local bindings.
Initial take on LLDB support.