internal/utils: Cleanup and IGL unification

With #64 and
#127 being merged, most
of the internal/utils package is moved to the IGL and can be removed
here. This is another step to unify our Go codebase.

Author: oxzi

notifications/plugin/plugin.go

@@ -6,8 +6,8 @@ import (
 	"errors"
 	"fmt"
 	"github.com/icinga/icinga-go-library/types"
+	"github.com/icinga/icinga-go-library/utils"
 	"github.com/icinga/icinga-notifications/internal/event"
-	"github.com/icinga/icinga-notifications/internal/utils"
 	"github.com/icinga/icinga-notifications/pkg/rpc"
 	"io"
 	"log"