change: improve interface translation
modified:
app/disp_callbacks.c - translate the shape name for the context menu
app/display.c - translate the shape name for the status bar
app/menus.c - translate the name of the tooltips for the menu
app/properties-dialog.c - translate the shape name for the title
lib/prop_text.c - fix empty object display name
plug-ins/pixbuf/pixbuf.c - fix problem with gettext
plug-ins/shape/shape.c - translate plugin description