Unsubscribe change notification API

Merge pull request #530 from elandau/bugfix/unregister_onChange

API to unsubscribe to property change notifications

Fix exception in config mapper with default value

Merge pull request #529 from elandau/bugfix/custom_mapper_default

Fix default value when using a custom mapper for a property.

Fix Java 7 <> Java 8 compatibility issue

• Fix Race Condition for null getProperty
• Fix Java 7 <> Java 8 compatibility issue

Property API refactor

Merge pull request #526 from elandau/feature/property_api_refactor

Refactor Property to use java8 functional APIs

Fix extra value change notification

Merge pull request #525 from elandau/bugfix/double_notification

Fix eager change notification

Avoid exception creation when a default value is provided.

Avoid exception creation when a default value is provided.

Fix ConfigurationSource ordering

Merge pull request #520 from elandau/bugfix/typo

fix: ConfigurationSource ordering

Fix static bridge listener

Merge pull request #518 from elandau/bugfix/typo

Improve initializing and reseting listeners in the static bridge

Fix typo in static bridge method name

Merge pull request #517 from elandau/bugfix/typo

Fix typo

Improved bridge to Archaius1

• Bridge commons configuration listeners to archaius2
• Remove those pesky DeploymentContext not initialized warnings
• Fix immutable config proxies returning null