Fix a crash reported by Axem related to freeing the dock list of an object.
This was caused by freeing the dock list from the destructor of an object which meant that copies of an object would corrupt the original object instance.
To make sure that doesn't happen again the copy constructor and assignment operator of object have been made private.

git-svn-id: svn://svn.icculus.org/fs2open@11158 387891d4-d844-0410-90c0-e4c51a9137d3
Revert 11158 as it breaks FRED compilation.

git-svn-id: svn://svn.icculus.org/fs2open@11159 387891d4-d844-0410-90c0-e4c51a9137d3