builds typesystem and rewriter examples.
added class scope to empty implementation
changed type misspelling
fixed example error.
added rw, ty examples to build
included rwperson
changed age to non-const and private

added const get_age to read the age, while setting the internal variable
to private to allow a assignment operator.
person is assigned ion do_rewrite.

1. get_rewriter do_rewrite assigns person to a new instance, to keep age
const.
2. do_rewrite also does not check if buffer is empty, as it should block.