Added wildcard and property placeholder support in SpringApplication

* When a config source is a String it can now be a pattern
* Default resource loaded in the BeanDefinitionLoader has been
changed to PathMatchingResourcePatternResolver;
* A check for the ResourcePatternLoader similar to that in
AbstractBeanDefinitionReader and property placeholder resolution
has been added to the load(CharSequence) method of the
BeanDefinitionLoader;
* Added a unit test illustrating the issue;