Add support for /v3/apps/:guid/actions/apply_manifest

[VaskoBozhurski]

Support for the following resource would be really useful when applying bulk changes to apps:
https://v3-apidocs.cloudfoundry.org/version/3.75.0/index.html#app-manifest

[dmikusa]

This will likely be resolved as part of #1103 since operations will need to use the v3 API for deployment. @pivotal-david-osullivan FYI.

Marking as an enhancement.