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/spec-example/specs/env.yaml

@@ -0,0 +1,12 @@
+apiVersion: fission.io/v1
+kind: Environment
+metadata:
+  name: python-27
+  namespace: default
+spec:
+  version: 2
+  builder:
+    command: build
+    image: fission/python-build-env-2.7:0.4.0rc
+  runtime:
+    image: fission/python-env-2.7:0.4.0rc