Roles drop down sorted by ID

closes #3391
- Changed sort order to ID instead of name
Rebind name and password to inputs on signup page

Closes #3410, Ref #3392
- Removed setting name from user email address per issue #3392
Create new user validator to DRY up validators

No issue
- Created NewUserValidator class to DRY up validation of a models name, email, and password
- Changed SignUpValidator to be an instance of NewUserValidator
- Changed SetUpValidator to extend NewUserValidator
Correct meta_title for author pages.

closes #3407
- Output correct meta_title for author pages
- Add test for meta_title for tag and author pages
Do not clear password until after leaving signin

Closes #3399
- Provide our own authenticate action handler which does not
  clear the password input.
- Use the Signin route's deactivate hook to clear the password
  property on the controller after the user has transitioned
  away from the signin page.
Merge pull request #3408 from jaswilli/issue-3399

Do not clear password until after leaving signin
Merge pull request #3411 from novaugust/signup-password

Rebind password to password input on signup page
Merge pull request #3412 from novaugust/credentials-validation-convergance

Create new user validator to DRY up validators
Merge pull request #3393 from joeldrapper/sort-roles-dropdown

Fixed role sort order in the invite a new user drop down list
Merge pull request #3413 from halfdan/3407-meta-title

Correct meta_title for author pages.
Implementing HTML emails

closes #3082
- adding HTML templates for "welcome", "reset password", and "invite user" emails (processed and unprocessed)
- created mail.generateContent() to create both HTML and plain-text versions of outgoing email
- refactored methods that trigger emails to send both HTML and plain-text emails