Adds login via token mechanism

- users update/create API accepts a new parameter called `token_login` that enables or disables the feature for a user
- when this feature is enabled, the user can only login by accessing a link that is sent to them by SMS. This link will log them in automatically without the need of entering other credentials. Regular login is not possible because nobody knows the user's actual password. 
- generated tokens are valid for 24 hours
- tokens can be regenerated - in this case the old token becomes invalid.

#6380

Gruntfile.js

@@ -480,7 +480,7 @@ module.exports = function(grunt) {
           `curl 'http://localhost:4984/_cluster_setup' -H 'Content-Type: application/json' --data-binary '{"action":"enable_single_node","username":"admin","password":"pass","bind_address":"0.0.0.0","port":5984,"singlenode":true}'`,
           'COUCH_URL=http://admin:pass@localhost:4984/medic COUCH_NODE_NAME=nonode@nohost grunt secure-couchdb', // yo dawg, I heard you like grunt...
           // Useful for debugging etc, as it allows you to use Fauxton easily
-          `curl -X PUT "http://admin:pass@localhost:4984/_node/nonode@nohost/_config/httpd/WWW-Authenticate" -d '"Basic realm=\\"administrator\\""' -H "Content-Type: application/json"'`
+          `curl -X PUT "http://admin:pass@localhost:4984/_node/nonode@nohost/_config/httpd/WWW-Authenticate" -d '"Basic realm=\\"administrator\\""' -H "Content-Type: application/json"`
         ].join('&& ')
       },
       'clean-test-database': {

admin/src/css/configuration.less

@@ -113,6 +113,10 @@ dl.horizontal {
     min-width: 100%;
     margin-left: -15px;
     margin-right: -15px;
+    table-layout: fixed;
+    td.break {
+      word-break: break-word;
+    }
   }
   td,
   th {