Create an Activty entity that stores activities of users.

[yavuzsa]

We decided to have an Activity table in the databse which holds the activities done by each user. The activity entity should contain userId, userName, userMedia, activityType, storyId, storyTitle, followindId, followingName and timestamp fileds.

[BurakKocak99]

thisi issue is resovled with commit 4bf19f3