Add 'EmailConfirmed' checking before sending notification emails when 'RequireConfirmedEmail' is true

Right now we only check the value of ```CanNotify``` on ```CoreWikiUser``` if we can send emails to a user.

We should also check the value of ```EmailConfirmed``` in the ```AspNetUsers``` table to detirmine if we can send emails to a user. This should take into account the value of the ```RequireConfirmedEmail``` application setting.

### Notification Emails

| EmailConfirmed | RequireConfirmedEmail | CanNotify | Action |
| ----------------- | -------------------------- | ----------- | ------- |
| False | False | False | Don't send |
| False | False | True | Send |
| False | True | False | Don't send |
| False | True | True | Don't send |
| True | False | False | Don't send |
| True | False | True | Send |
| True | True | False | Don't send |
| True | True | True | Send |

### Forgot Password Email

| EmailConfirmed | RequireConfirmedEmail | CanNotify | Action |
| ----------------- | -------------------------- | ----------- | ------- |
| False | False | N/A | Send |
| False | True | N/A | Don't send |
| True | True | N/A | Send |

### Confirmation Email

| EmailConfirmed | RequireConfirmedEmail | CanNotify | Action |
| ----------------- | -------------------------- | ----------- | ------- |
| False | False | N/A | Don't send |
| False | True | N/A | Send |
| True | True | N/A | N/A |