SPA: remove the signin and signout API

Bubbles up the API to the generic SPA interface.
SPA: add the setCredential method

setCredential send the credential to the SPA subworker.
It should be called before connect or autoconnect.
SPA: merge setCredentials, connect and autoconnect
HTTP: improve the error callbacks
SPA: implement reauth-needed.
Frontend tests: include a missing file
Add tests for reauth-needed.
Fix jshint error
Fix old autologin
SPA: improve test coverage
Merge branch 'master' into spa-connect-interface
Fix minor typo
Merge pull request #268 from tOkeshu/spa-connect-interface

Spa connect interface
Added TkWorker#closeSession()
Worker: removed _currentUserData global object, moved to tkWorker.currentUser
removed loading of removed test file
updated SPA tests to use new TkWorker#currentUser
renamed TkWorker#currentUser & TkWorker#currentUsers to user & users
renamed UserData#userName to UserData#name
Add ice candidate handling for the peer connections