3.0 template correction

This fixes several issue in the folders shown for missing plugins, components and helpers.

Personnaly, I would get rid of the differencies made beetween a loaded plugin and a not loaded plugin for the `$filepath` as the `Plugin::classPath()`method return a complete directory on the hardrive and this is not consistent with the other displayed directories.
i think taht using `$filePath = 'plugins' . DS . h($plugin) . DS . 'src' . DS;` as soon as `!empty($plugin)` is enought. let me know your point of view.