Rekonf: Switch to external service definition and implementation of simple reconfiguration

[durinfab]

This pr implements the external import of service declarations via json files. The read data get added to the neo4j database. This pr also provides a simple reconfiguration algorithm.

Notable changes the to the data structure of the ServiceEntry:

export type ServiceEntry = {
    type: string;
    uuid: string;
    mainDevices: [string]; //uuid of devices where the service wants to get messages from
    replacementDevices: [string]; //devicegroups of the main devices (to find replacement devices)
    room: string;
    configMsg: string;
    online: boolean;
};

devicegroups: types inside a device group are interchangeable and fulfil the same demands

What works:

• configure services with main and replacement configuration
• all necessary data is saved in the db
• import services and devicegroups and import them into the db
• Transfer of the current service state to the db
• automatic reconfiguration on offline-message