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/ops/podman.go

@@ -1,14 +1,14 @@
 package ops
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "podman",
 		Description: "Build an image using instructions from Containerfiles",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "events", Description: "Show podman system events"},
 			{Name: "info", Description: "Display podman system information"},
 			{Name: "inspect", Description: "Display the configuration of object denoted by ID"},
@@ -46,7 +46,7 @@ func init() {
 			{Name: "pod", Description: "Manage pods"},
 			{Name: "untag", Description: "Remove a name from a local image"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--add-host", Description: "Add a custom host-to-IP mapping (host:ip)"},
 			{Name: "--build-arg", Description: "Set build-time variables"},
 			{Name: "--cache-from", Description: "Images to consider as cache sources"},