Validate a Client. 

A Client attempts to authenticate by passing a Client username and password. 

If authentication is successful, a Token is generated. If authentication is unsuccessful, an empty token ('') is returned in the Token property. 

Many functions performing operations with sensitive data, require a Token and return a TAuthenticate Object. The Token generated in this function should be passed to other functions requiring a Token. 

This function is the same as ValidateUser. 

This function has security level "Public", and can be accessed by anyone without authentication.

[WebMethod(Description = "Validates an client's login and returns a token")]
public TAuthenticate ValidateClient(string sUsername, string sPassword);