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/README.md

@@ -0,0 +1,11 @@
+This is the root directory of a declaratively specified fission "application".  The app
+contains source code for one function (a simple "hello world") in the hello/hello.py
+file.
+
+The `specs` directory contains YAML files that specify the Fission environment and
+function.
+
+You can create this app on your cluster by running `fission spec apply` from this
+directory.  See `fission spec --help` for other options.
+
+After applying the spec, you can test the function with `fission fn test --name hello`.

examples/spec-example/hello/build.sh

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+#!/bin/sh
+
+set -e
+
+# check syntax
+python -m compileall -l ${SRC_PKG}
+
+# install deps
+pip install -r ${SRC_PKG}/requirements.txt -t ${SRC_PKG} && cp -r ${SRC_PKG} ${DEPLOY_PKG}

examples/spec-example/hello/hello.py

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+import yaml
+
+def main():
+    return "hello, world!!\n"

examples/spec-example/hello/requirements.txt

@@ -0,0 +1 @@
+pyyaml

examples/spec-example/specs/env.yaml

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+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

examples/spec-example/specs/fission-config.yaml

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+kind: DeploymentConfig
+name: spec-example
+uid: 27438a48-4191-4b5e-95b2-7793624317b9

examples/spec-example/specs/hello.yaml

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+apiVersion: fission.io/v1
+kind: Function
+metadata:
+  name: hello
+  namespace: default
+spec:
+  environment:
+    name: python-27
+    namespace: default
+  package:
+    packageref:
+      name: hello-pkg
+      namespace: default
+    functionName: hello.main
+
+---
+apiVersion: fission.io/v1
+kind: Package
+metadata:
+  name: hello-pkg
+  namespace: default
+spec:
+  source:
+    url: archive://hello-archive
+  buildcmd: "./build.sh"
+  environment:
+    name: python-27
+    namespace: default
+status:
+  buildstatus: pending
+
+---
+kind: ArchiveUploadSpec
+name: hello-archive
+include:
+  - "hello/*.py"
+  - "hello/*.sh"
+  - "hello/requirements.txt"