Add CloudFoundry EndpointHandlerMapping

[philwebb]

We need a variant of EndpointHandlerMapping that exposes actuator endpoints for Cloud Foundry to use.

The endpoints should be exposed under /cloudfoundryapplication and should be present regardless of user endpoint settings. In addition the mapping must handle security.

Tasks

• Add new endpoint handler mapping
• Add HAL like endpoint for discoverability
• Add CF security
  • Extract UAA url from CC's /info
  • Validate UAA token - get public keys from /token_keys, validate signature, issuer and expiry
  • Validate UAA token - validateAudience
  • Cache response to save multiple calls
• Make HealthMvcEndpoint show full details when accessed via /cloudfoundryapplication
• Enable by default
• Limit HAL based on ROLE