Add Email scalar

[clutcher]

Email validation is used almost in each application, so it could be reasonable to create an Email scalar.

But it is not so simple to define, what is a valid email. Technically there are RFC, which defines valid email, but regexp for that is massive, slow and covers cases, which people doesn't use. Here is an article about that.

Maybe there is morre sense to create an RegExpScalar and define few implementtation for email validations:

• Basic latin letters, numbers and special symbols like (+,_...)
• UTF-8 chars, numbers and special symbols (there are non latin domains)
• RFC compliant validation