Delete config properties

[Emily-Jiang]

As an application developer, deployer or tester or a framework developer or tester, I expect to be able to specify that a configuration property should be removed in the event that it would otherwise have a value, so that I can easily make necessary adjustments to the configuration at deployment or testing time.

Based on #27 (comment) with some modifications

[tomas-langer]

We need to decide (architecture) of handling this

• do we want to support this at all (maybe we can define configuration without the requirement to remove a property)
• if we want to support it, will it be an integral part of config source features or an external feature ("special" source to delete properties?)

This must be decided for 1.0