Refactor Project API to reflect changes upstream

projectile-project-root no longer returns `default-directory` if not in
a project (it returns nil). As such, doom-project-* functions (and their
uses) have been refactored.

+ doom-project-p & doom-project-root are aliases for
  projectile-project-p & projectile-project-root.
+ doom-project-{p,root,name,expand} now has a DIR argument (for
  consistency, since projectile-project-name and
  projectile-project-expand do not).
+ The nocache parameter is no longer necessary, as projectile's caching
  behavior is now more sane.
+ Removed some projectile advice/hacks that are no longer necessary.
+ Updated unit tests

modules/emacs/term/autoload.el

@@ -7,7 +7,7 @@ non-nil, cd into the current project's root."
   (interactive "P")
   (let ((default-directory
           (if arg
-              (doom-project-root 'nocache)
+              (or (doom-project-root) default-directory)
             default-directory)))
     ;; Doom's switch-buffer hooks prevent themselves from triggering when
     ;; switching from buffer A back to A. Because `multi-term' uses `set-buffer'
@@ -22,7 +22,7 @@ non-nil, cd into the current project's root."
   (interactive "P")
   (let ((default-directory
           (if arg
-              (doom-project-root 'nocache)
+              (or (doom-project-root) default-directory)
             default-directory)))
     (pop-to-buffer (save-window-excursion (multi-term)))))