More permissive e-mail validation

[robincyu]

The e-mail validation does not currently accept all valid e-mails. In particular, according to RFC 3696, e-mails such as "Fred Bloggs"@example.com, which contains whitespace, should be accepted as it is surrounded by quotes.

This change now accepts all e-mails of the form [any characters]@[any characters, the last of which is not a dot]. This is looser and allows invalid e-mails to pass, but it is better to allow some invalid e-mails to pass than to prevent someone from entering a valid e-mail. If stricter validation is needed, it may be preferable to use JavaMail which has a built-in validate() method.

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