engine: Resources package rewrite

This giant patch makes some much needed improvements to the code base.

* The engine has been rewritten and lives within engine/graph/
* All of the common interfaces and code now live in engine/
* All of the resources are in one package called engine/resources/
* The Res API can use different "traits" from engine/traits/
* The Res API has been simplified to hide many of the old internals
* The Watch & Process loops were previously inverted, but is now fixed
* The likelihood of package cycles has been reduced drastically
* And much, much more...

Unfortunately, some code had to be temporarily removed. The remote code
had to be taken out, as did the prometheus code. We hope to have these
back in new forms as soon as possible.

lang/funcs/engine.go

@@ -22,10 +22,10 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/purpleidea/mgmt/engine"
 	"github.com/purpleidea/mgmt/lang/interfaces"
 	"github.com/purpleidea/mgmt/lang/types"
 	"github.com/purpleidea/mgmt/pgraph"
-	"github.com/purpleidea/mgmt/resources"
 
 	multierr "github.com/hashicorp/go-multierror"
 	errwrap "github.com/pkg/errors"
@@ -103,7 +103,7 @@ func (obj *Edge) String() string {
 type Engine struct {
 	Graph    *pgraph.Graph
 	Hostname string
-	World    resources.World
+	World    engine.World
 	Debug    bool
 	Logf     func(format string, v ...interface{})
 
@@ -161,15 +161,15 @@ func (obj *Engine) Init() error {
 			return fmt.Errorf("vertex (%+v) was not an expr", vertex)
 		}
 
+		if obj.Debug {
+			obj.Logf("Loading func `%s`", vertex)
+		}
+
 		obj.state[vertex] = &State{Expr: expr} // store some state!
 
 		if e := obj.state[vertex].Init(); e != nil {
 			err = multierr.Append(err, e) // list of errors
 		}
-
-		if obj.Debug {
-			obj.Logf("Loading func `%s`", vertex)
-		}
 	}
 	if err != nil { // usually due to `not found` errors
 		return errwrap.Wrapf(err, "could not load requested funcs")