Improvements to kyaml fn framework

This commit creates a new version of the alpha configuration functions framework. Goals include:
- Make it easy to build multi-version APIs with the framework (not previously facilitated at all).
- Simplify the framework's APIs where redundant configuration options exist (leaving the most powerful, replacing others with helpers to maintain usability they provided).
- Make the Framework's APIs more consistent (e.g. between the various template types, usage of kio.Filter, field names)
- Decouple responsibilities (e.g. command creation, resource list processing, generation of templating functions).
- Make the framework even more powerfully pluggable (e.g. any kio.Filter can be a selector, and the selector the framework provides is itself a filter built from reusable abstractions).
- Improve documentation.
- Make container patches merge fields (notably list fields like `env`) correctly.

kyaml/fn/framework/command/testdata/standalone/config.yaml

@@ -0,0 +1,6 @@
+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
+
+apiVersion: example.com/v1alpha1
+kind: Foo
+a: b

kyaml/fn/framework/command/testdata/standalone/expected.yaml

@@ -0,0 +1,20 @@
+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
+
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: bar2
+  namespace: default
+  annotations:
+    foo: bar2
+    a: 'b'
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: bar1
+  namespace: default
+  annotations:
+    foo: bar1
+    a: 'b'

kyaml/fn/framework/command/testdata/standalone/input.yaml

@@ -0,0 +1,10 @@
+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
+
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: bar2
+  namespace: default
+  annotations:
+    foo: bar2