Ext.manifest or app.json (Package requirements)

So far i understood (hopefully correctly) that I need to specifiy required packages for my app in an "app.json" file. Somehow Sencha CMD could update my package folder then with the package. Now I did set up everything manualls in the past and still don't like the new folder and semi-automatisation in Sencha (I use Sencha Cmd in a ANT script and add to my "compile-classpath" the downloaded/unzipped extjs-lib folder).

Now, if I want to require the "sencha-core" in my ExtJS5 app, this package resides in the original extjs-lib folder. Does it mean I need to transfer this to my project folder or how do I get this src in my project folder? I've also seen that an app.json file would get configured with a requirements section for required packages. Is it also possible to use the Ext.manifest at the top of my code or is the app.json mandatory?

Example:

Code:

Ext.manifest = {
    framework: 'ext',
    compatibility: {
        ext: '5.0.0'
    },
    requires: [
        'sencha-core'
    ]
}

Sorry for this rather "dumb" questions...Sencha Cmd introduced too many options and is sometimes a bit of a black box to me still...