Support for Account approval proccess

[christianacca]

See https://github.com/brockallen/BrockAllen.MembershipReboot/issues/632

[christianacca]

PR summary

• [x] modify existing APIs:
  • add two methods to UserAccountService - ApproveAccount, RejectAccount
  • add two mapped DateTime? properties to UserAccount - AccountApproved, AccountRejected
  • add two computed properties to UserAccount - IsAccountApproved, IsAccountRejected
  • add two classes - AccountApprovedEvent, AccountRejectedEvent
  • add two overloads to EmailAccountEventsHandler for the two new event classes above
  • add MembershipRebootConfiguration.RequireAccountApproval
  • add SecuritySettings.RequireAccountApproval
  • add necessary MR constants to support above
  • obsolete MembershipRebootConfiguration.AllowLoginAfterAccountCreation
• [x] add additional localized validation messages
• [x] add email templates for the new events
• [x] add EF migrations for two new (nullable) columns in the UserAccount table
• [x] add tests for new feature and make all existing tests pass
• [x] ensure backwards compatibility

[christianacca]

Hi @brockallen, a decision needs to be made whether - feat(EmailNotification): send email when account is unlocked (or https://github.com/brockallen/BrockAllen.MembershipReboot/commit/277607b0b77d50c2356ea4d6449bdf0c4cb4e9bd) - over on master is a breaking change.

My gut feel is that it is a breaking change - the new emails that would be sent would not follow any branding customizations that maybe being applied by host app using MR.

If it is I'll update the nuspec files accordingly on master, then update this PR before merging into master...

If I don't here back (which is fine of course), I'll take a safe position and update the nuspec files to be a breaking change.