Session ids for different pseudobonds are identical

[Tom Goddard]

When I try to save a session with 3d labels on pseudobonds the label take_snapshot() data references the pseudobond which is saved using pbond._ses_id in Pseudobond.take_snapshot(). But the pbond._ses_id values I get for most of the pseudobonds are the identical (e.g. = 7) and session restore then fails to work correctly.

open 2gbp
label #1 pseudobonds
save test.cxs
close
open test.cxs

Sometimes this produces an error try to restore the pseudobond reference, sometimes it simply puts many of the labels on a single pseudobond.

[Eric Pettersen]

Okay, fixed this problem, but that uncovered another problem with pseudobond session identification. When the whole shebang is working, I'll close this.

[Eric Pettersen]

Needed to set up the pseudobond session IDs earlier in the save process since they may be asked for before the manager is actually saved.