Change JS alerts to inline messages OR dialog

[weboverhauls]

Support for JS alerts on Chromium is going away: https://developers.google.com/web/updates/2017/03/dialogs-policy

Dialog ref: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dialog

Instances (possibly remove some due to HTML5 required and server-side validation):

1. Sending tweet - content too long or null
2. Sending DM - user; content too long or null
3. Adding member to list
4. Creating/destroying a favorite
5. Creating/destroying a blocked user
6. Muting/unmuting a user
7. Uploading image
8. Creating a retweet
9. Following/unfollowing a user
10. Shortening URL

And confirm:

13. Delete list
14. Unsubscribe list
15. Report spammer
16. Block user
17. Delete DM
18. Deleting a list member
19. Deleting a tweet