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/config.lua

@@ -101,8 +101,5 @@ setmetatable(config.plugins, {
   end
 })
 
--- Disable these plugins by default.
-config.plugins.trimwhitespace = false
-config.plugins.drawwhitespace = false
 
 return config