lang: Initial implementation of the mgmt language

This is an initial implementation of the mgmt language. It is a
declarative (immutable) functional, reactive, domain specific
programming language. It is intended to be a language that is:

* safe
* powerful
* easy to reason about

With these properties, we hope this language, and the mgmt engine will
allow you to model the real-time systems that you'd like to automate.

This also includes a number of other associated changes. Sorry for the
large size of this patch.

resources/mgraph.go

@@ -150,7 +150,7 @@ func (obj *MGraph) Start(first bool) { // start or continue
 			unpause = false // doesn't need unpausing on first start
 			obj.wg.Add(1)
 			// must pass in value to avoid races...
-			// see: https://ttboj.wordpress.com/2015/07/27/golang-parallelism-issues-causing-too-many-open-files-error/
+			// see: https://purpleidea.com/blog/2015/07/27/golang-parallelism-issues-causing-too-many-open-files-error/
 			go func(vv pgraph.Vertex) {
 				defer obj.wg.Done()
 				// unset Worker() running flag just before exit