Enable the support for custom properties for the container_base generator.

[pwizenty]

Currently, container_base generator doesn't support the configuration of custom properties in operation models.

To enable the support of custom properties, the generator should be able to transform an operation aspect into a service property, as listed below.

// Operation aspect
aspect CustomProperty for containers, infrastructure {
    string key<mandatory>;
    string value<mandatory>;
 }

// Service property
service.property.key=service.property.value