atomspace: use TV shared_ptr

First rough draft; atomspace compiles, for now.
truthvlaue as shared_ptr: convert rest of opencog

Need to touch a lot of files to complete the conversion.
truth value shared_ptr conversion: UTests

convert all the utests to shared-ptr as well
oComposite TV test case bug fix
Another test case fix
truth value smart_ptr conversion: examples

Do the examples, as well.
Merge pull request #328 from linas/master

Convert truth values to use smart_ptr