Ezp 20654 ezflow cookie

# Description
I added a commit to https://github.com/ezsystems/ezflow/pull/46 to make it work also on browser with no localstorage support.

If localstorage is not available, we use a cookie. A cookie is written only for expanded blocks. So the bug should happen only on old browser with more than a 100 block expanded. I don't think that is a very common use case.

# Test
Manual test on firefox and IE7.