[web] fix os.rename usage on windows when destination exists os.rename on windows will raise OSError (or WindowsError subclass) when if destination file already exists. Also check that exception is EEXIST. There is an attempt to fix in f6ba947c but using IOError instead of OSError. Closes #14214794

[web/views] show composite entities in delete view Disabled by default, can be activated with show_composite = True Display first level of composite entities in a treeview, limited to the current (page_size - 1), so the maximum of displayed entities bump to page_size * (page_size - 1).