Update Datatypes, Attributes

Update Data Types :
1. Contact No. changed to String
2. Account No. Chaged to Int64

Attributes Addded :
1. Seen in Notification.
2. Draft Enum in ApticotEnums to represent Bill Status.
3. Is_active in Employee.

Update Constraint :
1. Bill_ID => PK in Bill_FM Table.
2. Bill_ID => PK in Bill_M Table

Now these tables contains Composite Primary Keys.

Corresponding changes in Document also.