Refactor trace guidance to avoid raw html in translations

Also rearrange to avoid multiple sentences in a heading.

app/views/traces/index.html.erb

@@ -76,5 +76,7 @@
 
   <%= render "trace_paging_nav", :page => @page, :page_size => @page_size, :traces => @traces, :params => @params %>
 <% else %>
-  <h4><%= t ".empty_html", :upload_link => new_trace_path %></h4>
+  <h2><%= t ".empty_title" %></h2>
+  <p><%= t ".empty_upload_html", :upload_link => link_to(t(".upload_new"), new_trace_path),
+                                 :wiki_link => link_to(t(".wiki_page"), t(".wiki_page_url")) %></p>
 <% end %>

config/locales/en.yml

@@ -2396,7 +2396,11 @@ en:
       public_traces_from: "Public GPS Traces from %{user}"
       description: "Browse recent GPS trace uploads"
       tagged_with: " tagged with %{tags}"
-      empty_html: "Nothing here yet. <a href='%{upload_link}'>Upload a new trace</a> or learn more about GPS tracing on the <a href='https://wiki.openstreetmap.org/wiki/Beginners_Guide_1.2'>wiki page</a>."
+      empty_title: Nothing here yet
+      empty_upload_html: "%{upload_link} or learn more about GPS tracing on the %{wiki_link}."
+      upload_new: Upload a new trace
+      wiki_page: wiki page
+      wiki_page_url: https://wiki.openstreetmap.org/wiki/Beginners_Guide_1.2
       upload_trace: "Upload a trace"
       all_traces: "All Traces"
       my_traces: "My Traces"

test/controllers/traces_controller_test.rb

@@ -756,7 +756,7 @@ class TracesControllerTest < ActionDispatch::IntegrationTest
     assert_template "index"
 
     if traces.empty?
-      assert_select "h4", /Nothing here yet/
+      assert_select "h2", /Nothing here yet/
     else
       assert_select "table#trace_list tbody", :count => 1 do
         assert_select "tr", :count => traces.length do |rows|