Split out the Package type into a first class Kubernetes resource (#295)

Split out the Package type into a first class Kubernetes resource. Before this change, packages were implicitly tied to functions.

This wasn't ideal because:
 * Functions will need to share packages
 * A package storage system may be more generally useful than just
   functions (for example, for storing static assets)

This change does the following:
* Updates the fission and tpr types to add a new Package and PackageSpec.  It also creates a PackageRef type, and a FunctionPackageRef type. The PackageRef simply references a package, but the FunctionPackageRef includes the name of a function within the package. This allows us to share packages between different functions.
* Updates fetcher and other components for first-class packages
* Allows customization of fetcher image pull policy in the helm charts

controller/api_test.go

@@ -27,7 +27,6 @@ import (
 
 	"k8s.io/client-go/1.5/pkg/api"
 
-	"bytes"
 	"github.com/fission/fission"
 	"github.com/fission/fission/controller/client"
 	"github.com/fission/fission/tpr"
@@ -83,8 +82,8 @@ func TestFunctionApi(t *testing.T) {
 		},
 		Spec: fission.FunctionSpec{
 			EnvironmentName: "nodejs",
-			Deployment: fission.Package{
-				Literal: []byte("code1"),
+			Deployment: fission.FunctionPackageRef{
+				FunctionName: "xxx",
 			},
 		},
 	}
@@ -94,22 +93,18 @@ func TestFunctionApi(t *testing.T) {
 	})
 	assertNotFoundFailure(err, "function")
 
-	m, err := g.client.FunctionCreate(testFunc)
+	_, err = g.client.FunctionCreate(testFunc)
 	panicIf(err)
 
 	_, err = g.client.FunctionCreate(testFunc)
 	assertNameReuseFailure(err, "function")
 
-	code, err := g.client.FunctionGetRawDeployment(m)
-	panicIf(err)
-	assert(bytes.Compare(code, testFunc.Spec.Deployment.Literal) == 0, "code from FunctionGetRawDeployment must match created function")
-
-	testFunc.Spec.Deployment.Literal = []byte("code2")
+	testFunc.Spec.Deployment.FunctionName = "yyy"
 	_, err = g.client.FunctionUpdate(testFunc)
 	panicIf(err)
 
 	testFunc.Metadata.Name = name2
-	m, err = g.client.FunctionCreate(testFunc)
+	_, err = g.client.FunctionCreate(testFunc)
 	panicIf(err)
 
 	funcs, err := g.client.FunctionList()
@@ -327,7 +322,7 @@ func TestMain(m *testing.M) {
 
 	go Start(8888)
 
-	time.Sleep(500 * time.Millisecond)
+	time.Sleep(time.Second)
 	g.client = client.MakeClient("http://localhost:8888")
 
 	resp, err := http.Get("http://localhost:8888/")