Package scanner

https://github.com/spring-projects/spring-framework/blob/49f3046f6637030743a1560f37245cd0dffc95a5/spring-core/src/main/java/org/springframework/core/io/support/PathMatchingResourcePatternResolver.java

This + some utils for class extraction would do for a neat package scanner.

Modularize spring-core into spring-core-io, spring-core-util, spring-core-resources (here will be package scanner) and spring-core