build(aio): big move of docs related files (#14361)

All the docs related files (docs-app, doc-gen, content, etc)
are now to be found inside the `/aio` folder.

The related gulp tasks have been moved from the top level
gulp file to a new one inside the `/aio` folder.

The structure of the `/aio` folder now looks like:

```
/aio/
  build/         # gulp tasks
  content/       #MARKDOWN FILES for devguides, cheatsheet, etc
    devguides/
    cheatsheets/
  transforms/    #dgeni packages, templates, etc
  src/
    app/
    assets/
    content/    #HTML + JSON build artifacts produced by dgeni from /aio/content.
                #This dir is .gitignored-ed
  e2e/           #protractor tests for the doc viewer app
  node_modules/ #dependencies for both the doc viewer builds and the dgeni stuff
                #This dir is .gitignored-ed
  gulpfile.js   #Tasks for generating docs and building & deploying the doc viewer
```

Closes #14361

aio/transforms/examples-package/services/parseArgString.js

@@ -0,0 +1,55 @@
+/**
+ * @dgService parseArgString
+ * @description
+ * processes an arg string in 'almost' the same fashion that the command processor does
+ * and returns an args object in yargs format.
+ * @kind function
+ * @param  {String} str   The arg string to process
+ * @return {Object} The args parsed into a yargs format.
+ */
+
+module.exports = function parseArgString() {
+
+  return function parseArgStringImpl(str) {
+    // regex from npm string-argv
+    //[^\s'"] Match if not a space ' or "
+
+    //+|['] or Match '
+    //([^']*) Match anything that is not '
+    //['] Close match if '
+
+    //+|["] or Match "
+    //([^"]*) Match anything that is not "
+    //["] Close match if "
+    var rx = /[^\s'"]+|[']([^']*?)[']|["]([^"]*?)["]/gi;
+    var value = str;
+    var unnammedArgs = [];
+    var args = {_: unnammedArgs};
+    var match, key;
+    do {
+      // Each call to exec returns the next regex match as an array
+      match = rx.exec(value);
+      if (match !== null) {
+        // Index 1 in the array is the captured group if it exists
+        // Index 0 is the matched text, which we use if no captured group exists
+        var arg = match[2] ? match[2] : (match[1] ? match[1] : match[0]);
+        if (key) {
+          args[key] = arg;
+          key = null;
+        } else {
+          if (arg.substr(arg.length - 1) === '=') {
+            key = arg.substr(0, arg.length - 1);
+            // remove leading '-' if it exists.
+            if (key.substr(0, 1) == '-') {
+              key = key.substr(1);
+            }
+          } else {
+            unnammedArgs.push(arg)
+            key = null;
+          }
+        }
+      }
+    } while (match !== null);
+    return args;
+  }
+}