Image resource refactor

This commit pulls most of the image related logic into its own package, to make it easier to reason about and extend.

This is also a rewrite of the transformation logic used in Hugo Pipes, mostly to allow constructs like the one below:

    {{ ($myimg | fingerprint ).Width }}

Fixes #5903
Fixes #6234
Fixes #6266

common/herrors/errors.go

@@ -52,6 +52,7 @@ func FprintStackTrace(w io.Writer, err error) {
 //     defer herrors.Recover()
 func Recover(args ...interface{}) {
 	if r := recover(); r != nil {
+		fmt.Println("ERR:", r)
 		args = append(args, "stacktrace from panic: \n"+string(debug.Stack()), "\n")
 		fmt.Println(args...)
 	}