[action/deploy/environment] Properly set @trace
[action/deploy/module] Consistent trace handling
[action/visitor] Extract visitor mixin

Only the action classes use the visitor pattern so the mixin is under
that namespace; if it's used elsewhere then the mixin should probably be
moved and generalized.
[action/deploy/environment] Refactor for visitor mixin
[action/deploy/module] Refactor for visitor mixin
[action/deploy/display] Extract to action class
Merge pull request #247 from adrienthebo/maint/master/deploy-actions

(GH-95) Clean up deploy actions, extract deploy/display action