Dataflow Server should download and save metadata

[corneil]

Problem description: When using deploy or update from ui there is a delay until the metadata has been downloaded. It seems the metadata is never caches and retrieved every time.

Solution description: The metadata for application that doesn't include SNAPSHOT in the version should be saved in the database for easy retrieval and can even be cached to reduce database impact. The query response from the browser can be assigned headers to ensure the browser caches the responses as well.