Add a Register time button to the time line

This button is most needed when viewing the interface on an extra small
screen, because in this case the register time first row will ben hidden.

stoptime.rb

@@ -1903,6 +1903,10 @@ module StopTime::Views
         text! "Timeline"
         small "#{@time_entries.count} time entries"
         div.btn_group.navbar_right do
+          a.btn.btn_default.btn_sm :role => "button", :href=> R(TimelineNew) do
+            _icon("time")
+            span "Register time"
+          end
           a.btn.btn_default.btn_sm.dropdown_toggle :role => "button",
             :href => "#", "data-toggle" => "dropdown" do
             _icon("filter")