[accessibility] more labels and alt tags

app/views/costlog/edit.rhtml

@@ -44,7 +44,7 @@
 
 <% content_for :header_tags do %>
   <%= javascript_include_tag 'editinplace', :plugin => 'redmine_costs' %>
-  <%= javascript_tag "initialize_editinplace('src=\"#{image_path('cancel.png')}\" value=\"#{l(:label_cancel)}\"' )" %>
+  <%= javascript_tag "initialize_editinplace('src=\"#{image_path('cancel.png')}\" value=\"#{l(:label_cancel)}\" alt=\"#{l(:button_cancel_edit_costs)}\" title=\"#{l(:button_cancel_edit_costs)}\"' )" %>
 
   <%= stylesheet_link_tag 'costs', :plugin => 'redmine_costs' %>
 <% end %>

app/views/groups/_users_unused.rhtml

@@ -14,7 +14,7 @@
         <td align="center" style="white-space: nowrap;">
           <% remote_form_for :group_user, group_user, :url => { :controller => 'groups', :action => 'set_membership_type', :id => @group, :user_id => user}, :method => :post  do |f| %>
             <%= f.select :membership_type, GroupUser::MEMBERSHIP_TYPES.collect{|t| [l(t), t]} %>
-            <%= image_submit_tag "save.png" %>
+            <%= image_submit_tag "save.png", :alt => l(:button_save) %>
           <% end %>
         </td>
         <td class="buttons">

config/locales/de.yml

@@ -165,4 +165,5 @@ de:
   caption_locked_on: "Gesperrt am"
   caption_show_locked: "Gesperrte Typen anzeigen"
   button_cancel_edit_budget: "Budget bearbeiten abbrechen"
+  button_cancel_edit_costs: "Kosten bearbeiten abbrechen"
   description_date_for_new_rate: "Datum für neuen Satz"

config/locales/en.yml

@@ -163,4 +163,5 @@ en:
   caption_locked_on: "Locked on"
   caption_show_locked: "Show locked types"
   button_cancel_edit_budget: "Cancel editing budget"
+  button_cancel_edit_costs: "Cancel editing costs"
   description_date_for_new_rate: "Date for new rate"