Disable trimwhitespace and drawwhitespace via their configs (#1446)

Instead of completely disabling them, we now use their internal toggle.

Also moved `drawwhitespace` commands inside the plugin.

---

* Fixed bug where commands would show even when plugin was disbled. Also removed antiquated way of disabling.

* Fixed typos.

* Also moved trimwhitespace out of config, if it already has a default enabled value of false.

* Changed documentation.

* Clarified comments.

data/core/command.lua

@@ -107,7 +107,7 @@ end
 function command.add_defaults()
   local reg = {
     "core", "root", "command", "doc", "findreplace",
-    "files", "drawwhitespace", "dialog", "log", "statusbar"
+    "files", "dialog", "log", "statusbar"
   }
   for _, name in ipairs(reg) do
     require("core.commands." .. name)