Implement POJOs for swatch-product-configuration

As a developer, I'd like to be able to use configuration from POJOs Java code, so that I can utilize configuration with idiomatic Java.

object models to be implemented:

Subscription:

• * platform: String
• * id: String
• requiredSubscriptions: List<String>
• includedSubscriptions: List<String>
• fingerprint: Fingerprint
• * variants: List<Variant>
• billingWindow: enum(MONTHLY)
• * metrics: List<Metric>
• defaults: Defaults

Fingerprint:

• engineeringIds: List<String>
• arches: List<String>

Variant:

• * tag: String
• roles: List<String>
• engineeringIds: List<String>
• productNames: List<String>

Metric:

• * id: String
• rhmMetricId: String
• awsDimension: String
• prometheus: PrometheusMetric
• billingFactor: Double
• uom (see later note)

PrometheusMetric:

• queryKey: String
• queryParams: Map<String,String>

Defaults:

• variant: String
• sla: enum(Standard, Premium, Self-Support)
• usage: enum(Development/Test, Production, Disaster Recovery)

Done:

• Subscription, FingerPrint, Variant, Metric, PrometheusMetric, and Defaults are implemented