Fixes and updates for some model and dal classes

1. Added back inheritance to Student, LocationApplication,
FundApplication, ClubUnregisterApplication and AssetApplication.
2. Added keyword virtual to some navigation properties enabling
lazy-loading.
3. Modified the context class so that it fits the inheritance and added
some code to process the inheritance mapping for the database.
Merge branch 'master' of https://github.com/ChocolateEleven/SCUT-Club-Management-System

Conflicts:
	SCUTClubManager.v11.suo
	SCUTClubManager/Models/AssetAssignment.cs
	SCUTClubManager/Models/ClubBranch.cs
	SCUTClubManager/Models/Student.cs