Property with default value from Supplier

[ljacqu]

Especially for beans it might be interesting to only have the default value be created if it's really needed, i.e. to supply a Supplier for the default value.

Downsides:

• fail-fast kind of breaks since a default value might be null from a Supplier and integrators don't notice it until it becomes relevant
• breaking change

Related:

• Prototype other way of handling properties #12
• Default values in configuration file #164