Refactor evaluation of doom!'s arguments

And update doom!'s docstring

core/core-modules.el

@@ -333,14 +333,15 @@ This value is cached. If REFRESH-P, then don't use the cached value."
 (defmacro doom! (&rest modules)
   "Bootstraps DOOM Emacs and its modules.
 
+If the first item in MODULES doesn't satisfy `keywordp', MODULES is evaluated,
+otherwise, MODULES is a multiple-property list (a plist where each key can have
+multiple, linear values).
+
 The bootstrap process involves making sure the essential directories exist, core
 packages are installed, `doom-autoload-file' is loaded, `doom-packages-file'
 cache exists (and is loaded) and, finally, loads your private init.el (which
 should contain your `doom!' block).
 
-If the cache exists, much of this function isn't run, which substantially
-reduces startup time.
-
 The overall load order of Doom is as follows:
 
   ~/.emacs.d/init.el
@@ -359,9 +360,10 @@ The overall load order of Doom is as follows:
 Module load order is determined by your `doom!' block. See `doom-modules-dirs'
 for a list of all recognized module trees. Order defines precedence (from most
 to least)."
-  `(let ((modules ',modules))
-     (unless (keywordp (car modules))
-       (setq modules (eval modules t)))
+  `(let ((modules
+          ,@(if (keywordp (car modules))
+               (list (list 'quote modules))
+             modules)))
      (unless doom-modules
        (setq doom-modules
              (make-hash-table :test 'equal