Remove Administration Email Address option, specify a user to be notified instead

[markkap]

The administration email is an orphan, set at site creation and neglected until there is notification that it needs to be verified, and even by then it might have already neglected for some time.

Effort of maintaining an up to date setting of administration email address is a duplication of maintaining up to date user email information, therefor it is better to abolish the option and replace it with an option at the administrators user's settings to receive administration email notification.

There could be several administrator receiving the administration email, but there must be at least one.

Value of admin_email option will be auto generated based on the email address of the relevant users, in first iteration, will use the "first" valid user found.

[markkap]

Need to consider how it will be played out on a multisite in which user has its information shared between sites.

probably a better strategy is to send emails to all administrator as there should be be more than one. (and for whoever uses the admin_email option give the email of the "first" administrator)