Add an API for about information

[nitisht]

Path: /api/v1/about

Response content:

{
	"version": "v0.6.0",
	"commit": "a35e07d",
	"deployment-id": "01H5F8KFHAEWJG183VFW9CQBNG",
	"update-available": true,
	"latest-version": "v0.6.1",
	"license": "AGPL-3.0-only",
	"mode": "local",
	"staging": "/parseable/staging",
        "store": "/parseable/data"
}