Refactor directive validity checks

Refactor directive validity checks

The check for the "replace" element appearing in a v1.1 directive is moved
to interpret_directive and directive processing no longer stops at the
first error, since the documentation states that the order of directive
elements is insignificant.

This also fixes a long-standing bug that resulted in the sending of email
to the registered maintainers for a package depending on the relative
location of the "directory" element; the testsuite is adjusted accordingly.