Fixing the email address property validation.

Fixing issue: http://issues.umbraco.org/issue/U4-5364

Also added appropriate code for Localization and added localization strings to the en & en_us language files.
Sorry, this is exactly why this isn't fixed yet... this can *never* happen.

Before this is fixed, the localization code needs to be ported over the Core library and then wrapped. It's been on the TODO list for quite some time and for some reason I cannot find the task for this.

Core can never reference *any* other library, it is the base core library. All of these other legacy libraries will eventually (one day) be removed.

Sorry but I need to close this PR because the localization core needs to be moved and wrapped before this can happen.