Declarative application specifications for Fission (#422)

This change enables users to have declarative specifications for Fission resources. Users can specify their "app" in a set of spec files, and use a new fission CLI command to "apply" these specs to a running cluster.

The new "spec" CLI also includes archiving of local source files, and a file watcher that re-builds archives and uploads them on file changes, and a package build watcher that waits for package builds on the CLI. 

A "--spec" option is also added to "function create", and will be added to other resources in future changes.  This option causes a YAML to be outputted to the specs directory instead of the resource being created on the cluster.

The CLI "fission spec --help" outputs usage information.

examples/go/specs/function-hello.yaml

@@ -0,0 +1,38 @@
+kind: ArchiveUploadSpec
+name: hello-go
+include:
+- hello.go
+
+---
+apiVersion: fission.io/v1
+kind: Package
+metadata:
+  creationTimestamp: null
+  name: hello-go-pkg
+  namespace: default
+spec:
+  environment:
+    name: go
+    namespace: default
+  source:
+    type: url
+    url: archive://hello-go
+status:
+  buildstatus: pending
+
+---
+apiVersion: fission.io/v1
+kind: Function
+metadata:
+  creationTimestamp: null
+  name: hello-go
+  namespace: default
+spec:
+  environment:
+    name: go
+    namespace: default
+  package:
+    functionName: Handler
+    packageref:
+      name: hello-go-pkg
+      namespace: default