D-Net

Update JWTGenerator.java with error checking about null fields

Add error checking for empty first ame, last name and role

Check if it is zombie user's username or email

Complete ldapmodify about zombies and users :P

Fix errors in emailExists and UsernameExists

Update ldap createUser with password parameter

Add EmailSender.java

Add usernameExists and emailExists

Fix a typo and Comment add password

make o attribute(institution) optional