Lecture discovery added

Student App
- NsdHelper class created
- Lecture discovery added
Lecture discovery patch
Lecture class placeholder

Lecture class created for development use in the rest of the program.
Needs to be implemented with its actual mechanics
StudentApp
 - Choose and connect to lecture implemented.
merging to update package name
Merge fixes
Student App
 - Socket connection with lecture
 - Sending Requests
 - Receiving Questions
Lecturer Network Module
- Server registration implemented.

(It seems to come up with errors from the OTHER app. They don't actually interfere with building the app, ignore unless it turns out worse.)
Lecturer Network Module
- sending Questions
- receiving Requests

Introduced Variables.java in Library, for shared constants etc.
Student Network module uses Variables.java
Lecturer: added Handlers for reporting network events back to the app
- Notification of student joining
- Requests
- Answers
Hopefully merged stuff. I'm praying.
Merge remote-tracking branch 'origin/master'