Partial fix (read questions please): Problems with copy-paste of nodes.

[nightmarebadger]

Partial fix for #255 and minor cleaning.

Moved the if for deleting self.request.session['kotti.paste'] out of the for loop so it's cleaner (we get rid of the count and enumerate(ids), plus we only need one if now instead of (n)).

Partially fixed #255 - we go through the nodes before we start copying now, which does help in some cases. The problem, however, persists if we not only delete some nodes, but after that add some new ones. When we paste, we will get the newly created nodes out of the database instead of the old ones.

PS: This is related to #257, but I separated them because I feel this is way more important (this can cause actual problems) then cleaning up the flash messages, especially because that one could take a while to get merged because of translations.

[dnouri]

If we can, maybe let's try to not reuse old IDs in our database. I think this would fix most of the problems here.

[nightmarebadger]

If possible, would not reusing old ID's during one server session be better? As in, we don't use old ID's, but after the server restarts (and the copy/paste info is lost anyway), we can again use all ID's.

This would probably be even more complicated though, and probably wouldn't bring all that much to the table (I doubt most Kotti sites would have enough content for the ID's to reach really high numbers). Will try to look into SQLAlchemy and see what options we have.

[dnouri]

I don't think we should care if those IDs will be reused after a server start or not. It won't matter.