alias install to bundle install

+ update help text.
I frequently do a duffle bundle list and then attempt to do a
duffle bundle install and it gives me an error because the command
to use is duffle install. This PR adds the install command under the
bundle cmd group to help with UX/making this easier for humans.

cmd/duffle/bundle.go

@@ -19,6 +19,7 @@ func newBundleCmd(w io.Writer) *cobra.Command {
 	}
 	cmd.AddCommand(
 		newBundleListCmd(w),
+		newInstallCmd(w),
 		newBundleShowCmd(w),
 		newBundleSignCmd(w),
 		newBundleVerifyCmd(w),

cmd/duffle/bundle_show.go

@@ -8,13 +8,22 @@ import (
 	"github.com/spf13/cobra"
 )
 
+const bundleShowShortUsage = `return low-level information on application bundles`
+
+type bundleShowCmd struct {
+	name     string
+	insecure bool
+	raw      bool
+	w        io.Writer
+}
+
 func newBundleShowCmd(w io.Writer) *cobra.Command {
 	bsc := &bundleShowCmd{}
 	bsc.w = w
 
 	cmd := &cobra.Command{
 		Use:   "show NAME",
-		Short: "return low-level information on application bundles",
+		Short: bundleShowShortUsage,
 		Long:  bsc.usage(true),
 		Args:  cobra.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -31,13 +40,6 @@ func newBundleShowCmd(w io.Writer) *cobra.Command {
 	return cmd
 }
 
-type bundleShowCmd struct {
-	name     string
-	insecure bool
-	raw      bool
-	w        io.Writer
-}
-
 func (bsc *bundleShowCmd) usage(bundleSubCommand bool) string {
 	commandName := "show"
 	if bundleSubCommand {

cmd/duffle/install.go

@@ -17,15 +17,17 @@ import (
 	"github.com/deislabs/duffle/pkg/repo"
 )
 
-const installUsage = `Installs a CNAB bundle.
+const installUsage = `Installs a Cloud Native Application Bundle (CNAB)
 
-This command installs a CNAB bundle with a specific installation name.
+This command installs a bundle with a specific installation name.
 A claim (a record about the application installed) is created during
 the install process and can be referenced by the installation name.
 Example:
 	$ duffle install my_release example:0.1.0
 	$ duffle status my_release
 
+Note: To install a bundle, use $ duffle bundle install or $ duffle install. They are aliases for the same action.
+
 Different drivers are available for executing the duffle invocation
 image. The following drivers are built-in:
 
@@ -84,7 +86,7 @@ func newInstallCmd(w io.Writer) *cobra.Command {
 
 	cmd := &cobra.Command{
 		Use:   "install [NAME] [BUNDLE]",
-		Short: "install a CNAB bundle",
+		Short: "install a bundle",
 		Long:  installUsage,
 		Args:  cobra.ExactArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {
@@ -100,7 +102,7 @@ func newInstallCmd(w io.Writer) *cobra.Command {
 	f.BoolVarP(&install.insecure, "insecure", "k", false, "Do not verify the bundle (INSECURE)")
 	f.StringVarP(&install.driver, "driver", "d", "docker", "Specify a driver name")
 	f.StringVarP(&install.valuesFile, "parameters", "p", "", "Specify file containing parameters. Formats: toml, MORE SOON")
-	f.StringArrayVarP(&install.credentialsFiles, "credentials", "c", []string{}, "Specify credentials to use inside the CNAB bundle. This can be a credentialset name or a path to a file.")
+	f.StringArrayVarP(&install.credentialsFiles, "credentials", "c", []string{}, "Specify credentials to use inside the bundle. This can be a credentialset name or a path to a file.")
 	f.StringArrayVarP(&install.setParams, "set", "s", []string{}, "Set individual parameters as NAME=VALUE pairs")
 	f.StringArrayVarP(&install.setFiles, "set-file", "i", []string{}, "Set individual parameters from file content as NAME=SOURCE-PATH pairs")
 

cmd/duffle/show.go

@@ -12,7 +12,7 @@ func newShowCmd(w io.Writer) *cobra.Command {
 
 	cmd := &cobra.Command{
 		Use:   "show NAME",
-		Short: "return low-level information on application bundles",
+		Short: bundleShowShortUsage,
 		Long:  bsc.usage(false),
 		Args:  cobra.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {