improve string and add comment for translators

gajim/dialogs.py

@@ -1487,7 +1487,7 @@ class FileChooserDialog(Gtk.FileChooserDialog):
 class AspellDictError:
     def __init__(self, lang):
         ErrorDialog(
-            _('Dictionary for lang "%s" not available') % lang,
+            _('Dictionary for language "%s" not available') % lang,
             _('You have to install the dictionary "%s" to use spellchecking, '
               'or choose another language by setting the speller_language '
               'option.\n\n'

gajim/roster_window.py

@@ -4535,6 +4535,7 @@ class RosterWindow:
                 # c_dest is None if jid_dest doesn't belong to account
                 return
             menu = Gtk.Menu()
+            #from and to are the names of contacts
             item = Gtk.MenuItem.new_with_label(_('Send %(from)s to %(to)s') % {
                 'from': c_source.get_shown_name(), 'to': c_dest.get_shown_name()})
             item.set_use_underline(False)