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

test/test_utils.sh

@@ -173,17 +173,24 @@ dump_fission_resources() {
     dump_fission_resource environment.fission.io    
 }
 
+dump_env_pods() {
+    fns=$1
+
+    echo --- All environment pods ---
+    kubectl -n $fns get pod -o yaml
+    echo --- End environment pods ---
+}
+
 dump_logs() {
     id=$1
 
     ns=f-$id
     fns=f-func-$id
 
+    dump_env_pods $fns
     dump_fission_logs $ns $fns router
     dump_fission_logs $ns $fns poolmgr
-
     dump_function_pod_logs $ns $fns
-
     dump_fission_resources
 }