airshipctl config (replace 686508)

This implementation creates named references between an airship
config file , and a user specified or system  default kubeconfig file

airshipconfig location can be specified via an envirnment variable
or via
--airshipconf string   Path to file for airshipctl configuration.
                       (default ".airship/config")

kubeconfig has to be explicitly stated using the argument below
--kubeconfig string    Path to kubeconfig associated with airshipctl
                       configuration. (default ".airship/kubeconfig")

if the argument is not specified a default empty kubeconfig will be
used using the default ".airship/kubeconfig"

All subcommands exposed via airshipctl config will update airship
config and airship related kubeconfig
when appropriate.

This patchset adds :

- Config Struct (type)
- config cmd and pkg
- get_cluster : List a specific name cluster or
                List all clusters if no name is provided.
- set-cluster : Create or Modify an existing cluster.

Review comment fixes as of Pathset 19
- Moved core functionality from cmd to pkg
- Encapsulate cmd needs in pck in nw files cmds, cmds_types and cmds_test .
  Expectation is that other functions will need func an structs there.
- added test for GetCluster
- Added GetCluster method to config object to be used by get_cluster command
- Change ClusterNames func as per review suggestion
- Change TestEmpty Cluster to avoid pointing to non test kubecnfig by default
- Change constant AirshipConfigFilePath to AirshipConfigDir
- Renamed config_utils to utils
- Added config cmd output tests
- Changes to settings_test.go to clean after itself.
- Created new pkg/config/testdata/GoldenString for struct data comparison values to avoid confusion
- Fix small get_cluster no name issue when empty config
- Fix issue when reconciling a cluster info that only exists in airship config and not in kubeconfig

Increased coverage to: SUCCESS: Test coverage is at 84.2%,
Started to move all testdata to a single place under pkg/config for now.

Change-Id: I7aae1f15afaebc99407f7fabccecf86ab0923bc3

cmd/testdata/TestRootGoldenOutput/rootCmd-with-defaults.golden

@@ -4,18 +4,19 @@ Usage:
   airshipctl [command]
 
 Available Commands:
-  argo        argo is the command line interface to Argo
   bootstrap   Bootstrap ephemeral Kubernetes cluster
   completion  Generate autocompletions script for the specified shell (bash or zsh)
+  config      Modify airshipctl config files
   document    manages deployment documents
   help        Help about any command
-  kubeadm     kubeadm: easily bootstrap a secure Kubernetes cluster
   kubectl     kubectl controls the Kubernetes cluster manager
   version     Show the version number of airshipctl
 
 Flags:
-      --debug   enable verbose output
-  -h, --help    help for airshipctl
+      --airshipconf string   Path to file for airshipctl configuration. (default "$HOME/.airship/config")
+      --debug                enable verbose output
+  -h, --help                 help for airshipctl
+      --kubeconfig string    Path to kubeconfig associated with airshipctl configuration. (default "$HOME/.airship/kubeconfig")
 
 Additional help topics:
   airshipctl cluster    Control kubernetes cluster

cmd/testdata/TestRootGoldenOutput/rootCmd-with-no-defaults.golden

@@ -8,7 +8,9 @@ Available Commands:
   version     Show the version number of airshipctl
 
 Flags:
-      --debug   enable verbose output
-  -h, --help    help for airshipctl
+      --airshipconf string   Path to file for airshipctl configuration. (default "$HOME/.airship/config")
+      --debug                enable verbose output
+  -h, --help                 help for airshipctl
+      --kubeconfig string    Path to kubeconfig associated with airshipctl configuration. (default "$HOME/.airship/kubeconfig")
 
 Use "airshipctl [command] --help" for more information about a command.

cmd/testdata/TestRootGoldenOutput/specialized-rootCmd-with-bootstrap.golden

@@ -9,7 +9,9 @@ Available Commands:
   version     Show the version number of airshipctl
 
 Flags:
-      --debug   enable verbose output
-  -h, --help    help for airshipctl
+      --airshipconf string   Path to file for airshipctl configuration. (default "$HOME/.airship/config")
+      --debug                enable verbose output
+  -h, --help                 help for airshipctl
+      --kubeconfig string    Path to kubeconfig associated with airshipctl configuration. (default "$HOME/.airship/kubeconfig")
 
 Use "airshipctl [command] --help" for more information about a command.