3.0 - Add plugin shell.

It symlinks / copies plugin's assets to app's webroot. Thought this might be handy to use in deployment tasks.

One issue I am having is with plugins with vendor namespace. The task first creates directory for vendor name and then proceeds to create symlink for the plugin's webroot inside it, but it fails resulting in folder being copied instead. 

If the directory for vendor name exists beforehand the symlink is created without problem. So for some reason php doesn't seem to realize the directory exists when it's created by the script itself. Using clearstatcache() doesn't help.
>Mod rewrite rules are beyond scope

I'm fine with that, probably shouldn't have mentioned them in the first place :)

> don't think we should try solving everyone's problem.

Alright, as long as it is clear *that* it happened (I can imagine people having problems if they upload an updated plugin asset, only to discover the file is not updated on the website, because that is using a copy)