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.

test/tests/test_spec_create/hello.py

@@ -0,0 +1,2 @@
+def main():
+    return "hello\n"

test/tests/test_spec_create/test_spec.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+
+#test:disabled
+
+set -euo pipefail
+
+fn=spec-$(date +%N)
+env=python-$fn
+
+# init
+fission spec init
+
+# verify init
+[ -d specs ]
+[ -f specs/README ]
+[ -f specs/fission-deployment-config.yaml ]
+
+# TODO replace with `fission env create --spec`
+cat > specs/env.yaml <<EOF
+apiVersion: fission.io/v1
+kind: Environment
+metadata:
+  name: $env
+  namespace: default
+spec:
+  version: 1
+  runtime:
+    image: fission/python-env:0.4.0
+EOF
+
+# create env
+fission spec apply
+trap "fission env delete --name $env" EXIT
+
+# verify env created
+fission env list | grep python
+
+# generate function spec
+fission fn create --spec --name $fn --env $env --code $(dirname $0)/hello.py
+
+# verify that function spec exists and has ArchiveUploadSpec, Package and Function
+[ -f specs/function-$fn.yaml ]
+grep ArchiveUploadSpec specs/*.yaml
+grep Package specs/*.yaml
+grep Function specs/*.yaml
+
+# create function
+fission spec apply
+trap "fission fn delete --name $fn" EXIT
+
+# verify function
+fission fn list | grep $fn
+
+sleep 3
+
+fission fn test --name $fn | grep -i hello
+
+