#332: Allow master configuration file for all tutorials

For #332.

I added a bunch of tests for tutorial/resolver.js too (i'll get round to filling out tests for tutorial.js eventually but i'll submit that as a separate pull request).

A .json file in the tutorials directory may be of the form:

```
{"title": "My TItle", "children": [ /* list of children */ ]}
```

in which case the file's name is used to connect the metadata with the tutorial (behaviour before this patch)

I've added the ability to specify multiple tutorial cnofigurations in one file like so:

```
{
  "sometopic" : {
    "title" : "Some Topic!",
    "children" : [
      "sometopicchild",
      "someothertopicchild"
    ]
  },
  "anothertopic" : {
    "title" : "etc"
  }
}
```

in this case, the JSON's file name is ignored and we use the object keys as the tutorial names (to match metadata to tutorials).

Additionally, one may specify a tutorial's metadata directly in the parent tutorial's 'children' attribute:

```
{
  "sometopic": {
    "title": "Some Topic!",
    "children": {
      "sometopicchild": {                 // <------
          "title": "Whatta Topic!"
      },
      "someothertopicchild": {
          "title": "You Gotta See This Topic!"
      }
    }
  }
}
```


I will put in a pull request for jsdoc3.github.com's tutorial page to update it, but what version would this change make it to? So that I can say "Since v3.??, you can also specify metadata for multiple tutorials in a single file ...."