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/oh_my_posh.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:        "oh-my-posh",
 		Description: "The config file to use",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "init", Description: "Initialize oh-my-posh for your shell"},
 			{Name: "get", Description: "Get oh-my-posh values"},
 			{Name: "shell", Description: "Get the current shell, example usage: 'oh-my-posh get shell'"},
@@ -27,7 +27,7 @@ func init() {
 			{Name: "NUM", Description: "The number of stacks"},
 			{Name: "version", Description: "Display the oh-my-posh version, example usage: 'oh-my-posh version'"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--config", Description: "The config file to use"},
 			{Name: "--format", Description: "The file format to use"},
 			{Name: "--print", Description: "Print the init script"},