Fix some issues with qtfred's ship list dialog

[MjnMixael]

Fixes a few things here:

1. Waypoints in the list were having their name copied with characters past the null terminator causing junk characters to appear in the string.
2. Waypoints were being pushed to the wing list in a clear copy/paste error.
3. Fix a heap crash by changing it so that objectSelectionChanged() no longer uses model()->match() which returns a QList. These QModelIndex objects are heap-allocated inside Qt's DLL, but freed by the CRT causing an MSVC debug heap boundary violation.