Added constants.
Refactored plugin communication.
Merge branch 'HEAD' of https://github.com/wpatrik14/ICTDroidLab.git

Conflicts:
	interfaces/src/hu/edudroid/interfaces/Plugin.java
	interfaces/src/hu/edudroid/interfaces/PluginEventListener.java
Removed unnecessary plugin components.
Adjusted WiFi plugin to new architecture.
Minor changes.