correct human-facing webId to WebID

[previously flagged](https://github.com/solid/node-solid-server/pull/1277/files#r307007501) in #1277

Author: TallTed

default-views/account/register-form.hbs

@@ -74,7 +74,7 @@
             <label class="control-label" for="externalWebId">External WebID:</label>
             <input type="text" class="form-control" name="externalWebId" id="externalWebId" value="{{externalWebId}}"/>
             <span class="help-block">
-              By connecting this account with an existing webId, you can use that webId to authenticate with the new account.
+              By connecting this account with an existing WebID, you can use that WebID to authenticate with the new account.
             </span>
           </div>