Ability to define custom destructorings

[yyoncho]

At this point, dash supports 4 different destructoring keyword (keys/hash/plist/alist) and from what I can see it will be not hard to add new keywords by providing a destructuring template(or macro?) to generate the getter.

Example usecases:

• &hash which checks whether the map is empty before applying gethash
• Custom destructuring for cl-defstruct, e. g.

(-let [(&my/struct slot1 slot2) value]
  ...)