Add user Feature & Fixup
TODO: not very stable.
User TODO:
 1. client-side check (e.g. email format; password format)
 2. retype password has some problems when using
 3. Details behind delete user is not yet complete.
 (How to deal with FK casade relationship? e.g.: user deleted affects project/device..)
 4. Handle with user_data properly..
 5. Register form to be planned later.
 Fixup:
 1. Correct logo show in project chating.
 2. Scroller in device_list and user_management for overflowed table.
 3. Menu bar hiding authorized operations, fixed wrong "file record" authority handling.
 new file:   Control/RegisterForm.cs
 new file:   DB/dbo/Tables/RegisterForm.sql
 modified:   DB/dbo/Tables/User.sql
 modified:   Global.asax.cs
 modified:   data/SeminarRecordHandler.ashx.cs
 modified:   data/login.ashx.cs
 modified:   data/project.ashx.cs
 modified:   media/image/default-avatar.jpg
 modified:   media/js/device.js
 new file:   media/js/user_management.js
 modified:   uc/Menu.ascx
 modified:   uc/Menu.ascx.cs
 new file:   user_management.aspx
 new file:   user_management.aspx.cs
 new file:   user_management.aspx.designer.cs
 modified:   user_profile.aspx