kyaml: refactor command documentation into .md files from go files

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cmd/config/docs/api-conventions/merge2.md

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+# Merge (2-way)
+
+  2-way merges fields from a source to a destination, overriding the destination fields
+  where they differ.
+
+  ### Merge Rules
+
+  Fields are recursively merged using the following rules:
+
+  - scalars
+    - if present only in the dest, it keeps its value
+    - if present in the src and is non-null, take the src value -- if `null`, clear it
+    - example src: `5`, dest: `3` => result: `5`
+
+  - non-associative lists -- lists without a merge key
+    - if present only in the dest, it keeps its value
+    - if present in the src and is non-null, take the src value -- if `null`, clear it
+    - example src: `[1, 2, 3]`, dest: `[a, b, c]` => result: `[1, 2, 3]`
+
+  - map keys and fields -- paired by the map-key / field-name
+    - if present only in the dest, it keeps its value
+    - if present only in the src, it is added to the dest
+    - if the field is present in both the src and dest, and the src value is
+      `null`, the field is removed from the dest
+    - if the field is present in both the src and dest, the value is recursively merged
+    - example src: `{'key1': 'value1', 'key2': 'value2'}`, 
+      dest: `{'key2': 'value0', 'key3': 'value3'}`
+      => result: `{'key1': 'value1', 'key2': 'value2', 'key3': 'value3'}`
+
+  - associative list elements -- paired by the associative key
+    - if present only in the dest, it keeps its value in the list
+    - if present only in the src, it is added to the dest list
+    - if the field is present in both the src and dest, the value is recursively merged
+
+  ### Associative Keys
+
+  Associative keys are used to identify "same" elements within 2 different lists, and merge them.
+  The following fields are recognized as associative keys:
+
+  [`mountPath`, `devicePath`, `ip`, `type`, `topologyKey`, `name`, `containerPort`]
+
+  Any lists where all of the elements contain associative keys will be merged as associative lists.
+
+  ### Example
+
+  > Source
+
+	apiVersion: apps/v1
+	kind: Deployment
+	spec:
+	  replicas: 3 # scalar
+	  template:
+	    spec:
+	      containers:  # associative list -- (name)
+	      - name: nginx
+	        image: nginx:1.7
+	        command: ['new_run.sh', 'arg1'] # non-associative list
+	      - name: sidecar2
+	        image: sidecar2:v1
+
+  > Destination
+
+	apiVersion: apps/v1
+	kind: Deployment
+	spec:
+	  replicas: 1
+	  template:
+	    spec:
+	      containers:
+	      - name: nginx
+	        image: nginx:1.6
+	        command: ['old_run.sh', 'arg0']
+	      - name: sidecar1
+	        image: sidecar1:v1
+
+  > Result
+
+	apiVersion: apps/v1
+	kind: Deployment
+	spec:
+	  replicas: 3 # scalar
+	  template:
+	    spec:
+	      containers:  # associative list -- (name)
+	      - name: nginx
+	        image: nginx:1.7
+	        command: ['new_run.sh', 'arg1'] # non-associative list
+	      - name: sidecar1
+	        image: sidecar1:v1
+	      - name: sidecar2
+	        image: sidecar2:v1