bugfix: Whenever deleting m_log, verify that it is not null. Change to null after delete.

This fixes a double-free in cases of inheritance.
Merge pull request #296 from Astron/bugfix/double-free-m_log

bugfix: Whenever deleting m_log, verify that it is not null. Change to null after delete.
MessageDirector: Bugfix; don't let failure to connect upstream pass silently.
net: Use different IP:port parsing strategy to support hostnames (which may have multiple IPs), default ports, etc.
net: Also update EventLogger/EventSender to use new hostname resolution.
EventLogger: Change default file extension to .log, not .csv.
Tests: Update config tests to check the new hostname and IPv6 address resolution behavior.
net: AddressUtils -> address_utils
net: Don't use try...catch for control flow.
Merge pull request #298 from Astron/enhancement/hostnames

Enhancement: Add support for hostnames (and more robust IP checking, too!)
Merge remote-tracking branch 'origin/master' into feature/mongodb-backend