Meshmoon: Make JSON a first class citizen in Tundra. New JSON configs.

**JSON core support**

* Adds `CoreJsonUtils.h` that has various functions to parse JSON to `QVariant` and to serialize `QVariant` to JSON.
* Adds new dependency QJson http://qjson.sourceforge.net/
 * Dependency build implemented for Windows and Mac.
 * Linux needs to be implemented before this can be merged as this is a core dependency.
 * Currently uses my fork because I had to do windows fixes. Sent to upstream here https://github.com/flavio/qjson/pull/34

**Core config JSON support**

* New `--config` support for JSON.
 * Easier to read and write config file format. Less to write compared to the XML format.
 * More flexible type support: Maps of command-to-value pairs, strings or string lists as command-only. Can write numbers as numbers not as `"60"` (although we still store everything as strings in framework).
* Added new `tundra.json` that "replaces" `plugins.xml` and `tundra-client.json` that "replaces" `viewer.xml`.
* Both XML and JSON parsing is supported by `--config` this does not break anything that is out there.
* **Did not** remove the .xml configs at this point. Id like to get feedback if JSON is flexible enough to express all our potential needs before that is done. Or if it looks like it's not enough the .json configs can be removed to not have overlap in the repo.
 * `plugins.xml` is still default loaded if no `--config` startup parameter is present!

**Rendering config JSON**

* New rendering config using JSON.
 * Single file that has both Ogre resource locations and Ogre plugins.
 * Single file for all platforms. Has `Common` sections that get processed on all platforms and platform spesific sections.
 * Support for defining `--headless` run rendering plugin. Even if in config can be overridden with `--direct3d9` and `--opengl`. Defined `RenderSystem_Headless` as the headless renderer for Windows.
 * Removed old ogre *.cfg files.
* Ability to pass in custom rendering configs with `--ogreConfig` startup parameter.
* Cleaned up OgreRenderingPlugin and Renderer code.

**New headless renderer**

I started working on a proper headless renderer at https://github.com/jonnenauha/ogre-headless-renderer. The currently used `RenererSystem_Null` is buggy (at least in debug mode) and it has a nasty GPL license for Tundra. The new `RenderSystem_Headless` is tailored for Tundra `--headless` usage and already working.

With this pull request Windows moves to use the new headless renderer. Build and config paths included. This plugin will be automatically used if defined in the Ogre config headless section. But even then can be overridden with `--direct3d9` and `--opengl`.

**Note on dependencies**

Linux build path still needs to be implemented using either package manager or from sources, see more at http://qjson.sourceforge.net/build/.