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/ykman.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:        "ykman",
 		Description: "Configure your YubiKey via the command line",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "list", Description: "List connected YubiKeys"},
 			{Name: "config", Description: "Enable or disable applications"},
 			{Name: "mode", Description: "Manage connection modes (USB Interfaces)"},
@@ -60,7 +60,7 @@ func init() {
 			{Name: "generate", Description: "Generate a self-signed X.509 certificate"},
 			{Name: "PUBLIC-KEY", Description: "File containing a public key. Use '-' to use stdin"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "-c", Description: "Check if YubiKey is in FIPS Approved mode (available on YubiKey 4 FIPS only)"},
 			{Name: "-h", Description: "Show info usage information"},
 			{Name: "-s", Description: "List available smart card readers"},