Extracted ContentCachingRequestWrapper and ContentCachingResponseWrapper

Issue: SPR-12477
Polishing
Latest dependency updates (Groovy 2.3.8, Apache HttpClient 4.3.6)
Default conversion support for EnumSet / EnumMap

Issue: SPR-12483
Polishing

Issue: SPR-12483
BeanWrapper auto-growing support for EnumSet / EnumMap

Issue: SPR-12483
Polishing