Test integration of Log in / Log out

[jikalousek]

Implement http requests regarding the new authentication system. Handle http response (save token).

• Create mock HTTP request;

• Replace mock request with request to real end-poitn;

[aperkaz]

The retrieved token should be stored using: http://stackoverflow.com/questions/12293662/is-it-possible-to-use-localstorage-in-htmlservice

[aperkaz]

Relevant information about HTTP request construction on google scripts: http://stackoverflow.com/questions/26615546/google-apps-script-urlfetchapp-post-file