cmake_test/asserts/asserts

This module simply includes all of the various assert modules, so one only has to include this file to have access to all CMakeTest asserts.

Most (but not all) assertions come in two flavors: an affirmative assert and a negative assert. For example:

` ct_assert_defined(AN_IDENTIFIER)       # Fails if AN_IDENTIFIER is not defined ct_assert_not_defined(AN_IDENTIFIER)   # Fails if AN_IDENTIFIER is defined `