remove wrong support for function beans in indexer

[martinlippert]

The current indexer has special support for beans that implement functional interfaces from java.util.function, which doesn't really make sense. Instead, the indexer should treat @Bean methods that return a bean of such a type as a regular bean definition. In addition to that, indexing random type declarations that implement those functional interfaces as beans doesn't make sense, since those types are not automatically converted into beans at runtime.

This also means the remove the @> symbol prefix for functional beans and use @+ for bean definitions consistently.