Added Questing system

[Caragicu-Robert-Andrei]

Added by: Caragicu Robert Andrei
This is the base for a questing system. The system works with Unity ScriptableObjects so the quests, quest goals and rewards can be created as assets in the Unity project. During gameplay the QuestManager class is used to track quests.
Developers to create new goals they create classes which inherit Goal. When a player starts a quest the class returns an instance of type GoalProgress which tracks the progress for that specific goal. Progress is made when the player makes deeds which are classes that inherit the class Deed.
After the quest's goals are completed the quest awaits rewards. During gameplay the developer can choose when to give the rewards for the player and complete the quest. Rewards inherit the base class Reward which has a function that rewards the player in a specific way.

The pull request contains a demo scene which shows two quests.
The initial scene where the player must click to get quests

After the player clicks on first quest

After the player solves the first quest

After the player gets the rewards for the first quest

After the player clicks on second quest

After the player solves the second quest

After the player gets the rewards for the second quest