Add support for Cockpit CMS

[piotr-cz]

@this PR adds support for custom Cockpit CMS modules that are installed in [cockpit-path]/modules/addons/ folder. There is no support for core modules, which are distributed with the platform at the moment.

Module's composer.json file should contain the type: "cockpit-module" and name: "vendorName/cockpit-moduleName".

If you've installed Cockpit into other directory than cockpit or directory under root like public/cockpit, specify it's path in root composer.json file like so

"extra": {
    "installer-paths": {
        "public/cockpit/modules/addons/{$name}": ["type:cockpit-module"]
    }
}

Same installer can be used for cockpit-next and cockpit installation inside cocopi-kickstart.

@aheinze

I'm not sure how if the added $prefix parameter in the Lime\App::loadModules method you introduced in agentejo/cockpit@73552f3 can add possibility to change module name creation