Polish assertions and Javadoc for ResourceDatabasePopulator
Polish ModelFactory
Add dependency ordering for @ModelAttribute methods

Before this change @ModelAttribute methods were not invoked in any
particular order other than ensuring global @ControllerAdvice methods
are called first and local @Controller methods second.

This change introduces a simple algorithm that selects the next
@ModelAttribute method to invoke by making a pass over all methods and
looking for one that has no dependencies (i.e. @ModelAttribute
input arguments) or has all dependencies resolved (i.e. available in
the model). The process is repeated until no more @ModelAttribute
methods remain.

If the next @ModelAttribute method cannot be determined because all
remaining methods have unresolved dependencies, the first available
method is picked anyway just as before, i.e. with required
dependencies created through the default constructor.

Examples in ModelFactoryOrderingTests.

Issue: SPR-6299