Improvements to user Login field

[B]1. Add Validation of user Login field by Regular Expression[/B]

a. Validate Login field by Regular Expiration hard-coded in users_config.php (allow alpha-numeric symbols and "_", "-", "." symbols ONLY - that all symbols won't break url, when used in mod-rewrite).

b. To prevent issues with Login for all existing users - add OldStyleLogin field to PortalUser table and set it to 1 for users, whose Login field doesn't match new style logins.

For users, who have OldStyleLogin field set don't perform Login field validation. Perform Login field validation for new user registrations.

Based on OldStyleLogin field make Login field editable on my profile page.

All mentioned above should happen, when "email as login" option is enabled.

[B]2. Remove copying of Email into Login field when EmailAsLogin is selected[/B]

We have 2 login modes:

• by email
• by login

In case, when "EmailAsLogin" configuration is enabled, then email is copied into login field.

Since we add validation to login field (described above), then we shouldn't validate it when email is copied there. Also email coping seems a bit odd, so we should NOT copy email into Login field at all.

Make sure to check all themes and corresponding places in the code