WebSocket proxy support and Grunt proxy handling improvements



See merge request !28

`api.path=/api` has to be set in `arsnova.properties` for ARSnova
Backend.

Change Freetextchecker button semantics

The text label now says 'Worauf soll bei der strikten Prüfung geachtet werden?' instead of 'Worauf soll bei der strikten Prüfung nicht geachtet werden?'.
The semantics of the button underneath are now turned around.

See merge request !27

Initialization code for WebSocket connections has been simplified.
Support for socketioPath setting has been added. This allows WebSocket
connections through proxy servers.

The splash screen incorrectly checks for the existence of the global var
`ARSnova` which can, depending on loading speed, cause a ReferenceError.

Builds no longer depend on a preexisting config in ~/.ssh.

Implements the ability to check free text answers for correctness.

Closes !18
Refs !14, !22

swap subject and timestamp in feedback message view



See merge request !26

`tabbar-button-icon-color` is no longer bound to `smiley-bg-color`.

This fixes a regression introduced in
410a9f0a.

SessionInfo integration for session import

When importing a session, the "public pool" attributes are handled, too, to populate the session info.

See merge request !23

Fixes title bar for login panel.

Independent slides feature

Slides can now be enabled as part of custom feature selection in
arbitrary combinations with other features. With slides enabled and
question features disabled, question formats apart from 'slide' are
hidden. Some refactoring in feature controller and related code was
necessary to make the indepent feature selection possible.

See merge request !21