username and email check during register

[narayansiddhu]

username and email id validation during register a new user , whether the email and username are already taken are not.

[narayansiddhu]

while registering a new user with one username and email id with lower case , then if we try to use those same username and mail id with upper case it won't allow to register

[narayansiddhu]

i hope it is some what useful.Please validate and merge the code....!!!!