[core.specs] Improve names in core macro specs

Upon review, there are names and predicates in the existing core macro specs that could be more helpful when examining spec errors. The attached patch contains a number of name improvements. Most of these relate to path names within specs, more than are worth listing here (see the patch instead).

There are a few other changes of note:

• Spec name changes (tried to minimize these): ::arg-list -> :aram-list, ::args+body -> :arams+body

• Added even-number-of-forms? predicate

• Changed import list spec to be [package class+] instead of [package class*] to catch errors like (:import [java.util.Date]).

Patch: clj-2395.patch