upgrade httpcore and httpclient for outbound connections to version 5

NXRM 3.30.1 uses Apache httpclient version 4.5.13

httpclient version 5 is available and includes among other things:

• Redesigned connection pool implementation with strict connection limit guarantees.
  The connection pool is expected to have a better performance under higher concurrency
  due to reduced global pool lock contention.

• New connection pool implementation with lax connection limit guarantees and better
  performance under higher concurrency due to absence of a global pool lock.

https://github.com/apache/httpcomponents-core/blob/master/RELEASE_NOTES.txt

Usual regression testing and refactoring is expected.