[Completes #39645227] Admin can create a new app using Rails Admin
[Completes #40856241] Update error message file with new error messages
[Completes #40948835] Copy update: Tell Us a Little About Yourself task block
[Completes #39708075] User enters profile information with confidence because page contains legalease
[Completes #40631935] User receives email notification after deleting their account
Tweeks to /discovery layout.

Minor tweaks to span.welcome
[Completes #43135091] Developer goes to /discovery page and sees developer copy and is delighted

Added developer content to /discovery

Added developer link to footer links partials
Fixed problem with 404 and 500 page boxes.
Streamlined home page.
Centered footer text, fixed background issue on home page.
Fixed alignment issue with sign in button on home page.