Add links to the ToU and include them in signup

- 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

config/locales/en.yml

@@ -1089,6 +1089,8 @@ en:
     partners_ucl: "UCL"
     partners_bytemark: "Bytemark Hosting"
     partners_partners: "partners"
+    intro_tou_html: "Use of this site is subject to our %{tou_link}." 
+    tou: "Terms of Use"
     osm_offline: "The OpenStreetMap database is currently offline while essential database maintenance work is carried out."
     osm_read_only: "The OpenStreetMap database is currently in read-only mode while essential database maintenance work is carried out."
     donate: "Support OpenStreetMap by %{link} to the Hardware Upgrade Fund."
@@ -1299,7 +1301,7 @@ en:
         This site and many other related services are formally operated by the
         <a href='https://osmfoundation.org/'>OpenStreetMap Foundation</a> (OSMF)
         on behalf of the community. Use of all OSMF operated services is subject
-        to our <a href="https://wiki.openstreetmap.org/wiki/Acceptable_Use_Policy">
+        to our <a href="https://wiki.osmfoundation.org/wiki/Terms_of_Use">Terms of Use</a>, <a href="https://wiki.openstreetmap.org/wiki/Acceptable_Use_Policy">
         Acceptable Use Policies</a> and our <a href="https://wiki.osmfoundation.org/wiki/Privacy_Policy">Privacy Policy</a>
         <br>
         Please <a href='https://osmfoundation.org/Contact'>contact the OSMF</a>
@@ -2025,10 +2027,14 @@ en:
       terms declined: "We are sorry that you have decided to not accept the new Contributor Terms. For more information, please see <a href=\"%{url}\">this wiki page</a>."
       terms declined url: https://wiki.openstreetmap.org/wiki/Contributor_Terms_Declined
     terms:
-      title: "Contributor terms"
-      heading: "Contributor terms"
-      read and accept: "Please read the agreement and press the agree button to confirm that you accept the terms of this agreement for your existing and future contributions."
-      consider_pd: "In addition to the above agreement, I consider my contributions to be in the Public Domain"
+      title: "Terms"
+      heading: "Terms"
+      heading_ct: "Contributor terms"
+      read and accept: "Please read the contributor agreement and the terms of use, check the checkbox when done and then press the agree button to confirm that you accept the terms of both documents." 
+      contributor_terms_explain: "This agreement governs the terms for your existing and future contributions."
+      tou_explain: "These terms govern the use of the website and other infrastructure provided by the OSMF."
+      read_tou_html: "I have read and agree to the %{tou_link}"
+      consider_pd: "In addition to the above, I consider my contributions to be in the Public Domain"
       consider_pd_why: "what's this?"
       consider_pd_why_url: https://www.osmfoundation.org/wiki/License/Why_would_I_want_my_contributions_to_be_public_domain
       guidance: 'Information to help understand these terms: a <a href="%{summary}">human readable summary</a> and some <a href="%{translations}">informal translations</a>'