Add ability to register notifications to login server

[#77585216] https://www.pivotaltracker.com/story/show/77585216
Document setting up a local notifications service
Add ability to send a password reset notification to login server

[#77585238] https://www.pivotaltracker.com/story/show/77585238

Signed-off-by: Madhura Bhave <mbhave@gopivotal.com>
Register notifications at the time of first usage if not pre-registered

[#77585238] https://www.pivotaltracker.com/story/show/77585238
Refactor the email service to have a common interface for notifications and SMTP
- EmailPasswordResetService uses the appropriate messageService to send emails

[#78676824] https://www.pivotaltracker.com/story/show/78676824

Signed-off-by: Madhura Bhave <mbhave@gopivotal.com>
Connection error from notifications server only ignored on startup

- Also, don't provide default value for notifications.url

[#77585216] https://www.pivotaltracker.com/story/show/77585216

Signed-off-by: Madhura Bhave <mbhave@gopivotal.com>
Update uaa submodule pointer

Signed-off-by: Madhura Bhave <mbhave@gopivotal.com>
Merge branch 'feature/notifications' into develop