Support user assertion predicates as simple function for CppUnit 2

Currently to define a new assertion, the user is required to define both a new macro and a C function this macro forward to. Change it so defining a new assertion is as simple as definition a new C function.

Interface Minimization for CppUnit 2

The current interface is spread over multiple headers, often made more complex due to the presence of implementation details. The implementation should be isolated using "implementation" details headers or the pimpl idiom.

Replace TestSuite factory with TestCaseFactory for CppUnit 2

Currently, all test cases must be instantiated at registration. This as a drawback with regards to memory consumption, and complexify significatively the interface as care is required for dealing with memory management. It as also made implementation of parametrized test cases complex. Instead of providing direct ac...