- this adds links to the ToU in the Welcome box and on the About page
- adds a timestamp column to the users table to record acceptance of the ToU
- require ToU to be accepted before signup can proceed
- rearrange and change text on signup page
To avoid Chrom getting upset about sending form data to sites
that our policy doesn't allow, even when it isn't, use Javascript
to jump straight to Omniauth as the direct OpenID based login
buttons were already doing.
Fixes#1909
