Created start layout for internal area with login and shop management

[mennthor]

Start route for internal area is now /login.
No proper credential handling is included, only mockup.
On successful login, internal landing area is shown.
User can got to new shop registration or shop management for existing shops from there.

[maxnoe]

POST to /api/login using ajax and check return code (200 = authenticated, 401 not authenticated).
It also provides info what the reason for the denial is (wrong_credentials or a missing_role.)

[maxnoe]

import JQuery from 'jquery'
JQuery.ajax(
    '/api/login',
    {
         method: "POST",
         data: {username: this.username, password: this.password},
         success: () => {handle sucess case here},
         error: (response) => {handle error case here}
    }
)