Clean Luigi store

[JohannesDoberer]

We do not clear the subscriptions that we store in Luigi store. That leads to multiple initialization of route handling.

How to reproduce:
Browser console:

var cfg = Luigi.getConfig();
Luigi.unload();
Luigi.setConfig(cfg);
Luigi.unload();
Luigi.setConfig(cfg);

Result:
=> navigate: luigi-client did not respond, using fallback by replacing iframe

Root cause:
How to check the multiple initialization of route handling:

1. add a console log here console.log('enableRouting')
2. start simpledev
3. browser console

var cfg = Luigi.getConfig();
Luigi.unload();
Luigi.setConfig(cfg);
Luigi.unload();
Luigi.setConfig(cfg);

// when you do this more often you will see an increase of the console logs 'enableRouting'
Luigi.unload()
Luigi.setConfig(cfg);
Luigi.unload()
Luigi.setConfig(cfg);
....

[walmazacn]

Clearing Luigi store works as expected - small unit test would be helpful

[walmazacn]

Looks good