ChRIS UI: Idea for login screen / retrieve password design

Just some simple tweaks to the v1 of the login screen. A little changelog here:

- **Username => email address** - not sure if this is ok, but thought it would simplify things so users wouldn't have to remember a username; it's could be easier to ask for email address for password reset / retrieval because often users forget their username and you can avoid that.
- **Colored primary action button** - just to draw a little more attention to the primary button on the screen. Log in for front, reset password for reset pass screen.
- **CAPTCHA for password reset** - just a silly idea. Don't know how password reset mechanism works, I was guessing it could email a temporary / time-limited pass or login URL that would then prompt the user to change password using a standard password reset page.
- **footer credits** - was thinking this could go in the main UI too. Since part of the purpose of the UI for the hackathon is to get plugin devs familiar with the CHRIS project, just a tiny bit more information about everyone working on it.
- **big bold logo** - maybe too much :)