refactor(commands): separate commands and its core into two folders (#32)

- I think it would be better if one for commands only, one for the spec
handling core logic so people won't be confused by the core logic inside
the commands folder (cleaner I guess)
- Regen docs

commands/sys/shell_config.go

@@ -1,14 +1,14 @@
 package sys
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "shell-config",
 		Description: "Display help for command",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "install", Description: "Install MacOS setup with Multi-Selection"},
 			{Name: "shell", Description: "Setup a shell configuration with a robust set of tools and architecture"},
 			{Name: "update", Description: "Update the CLI to the latest version"},
@@ -20,7 +20,7 @@ func init() {
 			{Name: "delete", Description: "Delete external shell"},
 			{Name: "help", Description: "Display help for command"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-h", Description: "Display help for command"},
 			{Name: "-t", Description: "Select update version"},
 			{Name: "-m", Description: "Daemon check for update notification. When specified is true"},