The copy/pasting of dive-sites was fundamentally broken in at least two
ways:
1) The dive-site pointer in struct dive was simply overwritten, which
breaks internal consistency. Also, no dive-site changed signals where
sent.
2) The copied dive-site was stored as a pointer in a struct dive. Thus,
the user could copy a dive, then delete the dive-site and paste.
This would lead to a dangling pointer and ultimately crash the
application.
Fix this by storing the UUID of the dive-site, not a pointer.
To do that, don't store a copy of the dive, but collect all
the data in a `dive_paste_data` structure.
If the dive site has been deleted on paste, do nothing.
Send the appropriate signals on pasting.
The mobile version had an additional bug: It kept a pointer to the
dive to be copied, which might become stale by undo.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
