Allow swapping the position of other elements in the map

[codestiff]

(defn assoc-after [map key assoc-key assoc-val])
(defn assoc-before [map key assoc-key assoc-val])
(defn swap-position [map key1 key2])
(defn swap-after [map key-to-be-after key2])
(defn swap-before [map key-to-be-before key2])