added initial version of the POP3 module
Update James Protocols POP3 with string based UIDL support. Added Base64
encoding for POP3 UIDL of UUID.
Major part of POP3 commands implemented
Added configuration options for POP3
Added POP3 integration tests
Added more POP3 integration tests.
Add configurable LMTP delivery to POP3. Update integration tests.
Added POP3 authentication.