Delete the default copy and move operations

For Basic instances, the default copy and move operations are not defined (by
default), so we explicitly remove them. Now code like this fails:

Integer i, j; // Fails
i = j; // Fails (even if the previous line succeeded)

So the user is forced to use RCP<Integer> for copies as intented.
Fix Symbol's test not to use copy constructors

Now when default copy and move operations are deleted, this test fails (as it
should), because it uses the unsupported operations. We fix it to use RCP, now
things work.