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.

engine/fs.go

@@ -0,0 +1,61 @@
+// Mgmt
+// Copyright (C) 2013-2018+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package engine
+
+import (
+	"os"
+
+	"github.com/spf13/afero"
+)
+
+// from the ioutil package:
+// NopCloser(r io.Reader) io.ReadCloser // not implemented here
+// ReadAll(r io.Reader) ([]byte, error)
+// ReadDir(dirname string) ([]os.FileInfo, error)
+// ReadFile(filename string) ([]byte, error)
+// TempDir(dir, prefix string) (name string, err error)
+// TempFile(dir, prefix string) (f *os.File, err error) // slightly different here
+// WriteFile(filename string, data []byte, perm os.FileMode) error
+
+// Fs is an interface that represents this file system API that we support.
+// TODO: this should be in the gapi package or elsewhere.
+type Fs interface {
+	//fmt.Stringer // TODO: add this method?
+	afero.Fs     // TODO: why doesn't this interface exist in the os pkg?
+	URI() string // returns the URI for this file system
+
+	//DirExists(path string) (bool, error)
+	//Exists(path string) (bool, error)
+	//FileContainsAnyBytes(filename string, subslices [][]byte) (bool, error)
+	//FileContainsBytes(filename string, subslice []byte) (bool, error)
+	//FullBaseFsPath(basePathFs *BasePathFs, relativePath string) string
+	//GetTempDir(subPath string) string
+	//IsDir(path string) (bool, error)
+	//IsEmpty(path string) (bool, error)
+	//NeuterAccents(s string) string
+	//ReadAll(r io.Reader) ([]byte, error) // not needed
+	ReadDir(dirname string) ([]os.FileInfo, error)
+	ReadFile(filename string) ([]byte, error)
+	//SafeWriteReader(path string, r io.Reader) (err error)
+	TempDir(dir, prefix string) (name string, err error)
+	TempFile(dir, prefix string) (f afero.File, err error) // slightly different from upstream
+	//UnicodeSanitize(s string) string
+	//Walk(root string, walkFn filepath.WalkFunc) error
+	WriteFile(filename string, data []byte, perm os.FileMode) error
+	//WriteReader(path string, r io.Reader) (err error)
+}