Remove unused 'lib' files and modules

[kriegaex]

• Of beanutils, collections, digester and logging actually only digester and logging are directly used in AspectJ code. Therefore, remove the unused ones and upgrade the remaining libraries' versions to ones which also have source JARs on Maven Central. This makes downloading sources from GitHub and packaging separate commons.jar and commons-src.zip artifacts superfluous. Hence, we can get rid of them completely.
• Remove unused BCEL libraries and verifier source code
• Remove unused regex library
• Remove unused jarjar library
• Remove redundant JDT Core copy in lib folder