Add support for Location serialization

Description
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The unity-js-scopes package have a minimal set of tests associated with a few of the features exposed in the Javascript Scopes API it exposes. Those tests need to be expanded.

This bug targets the binding to the Location class that lacks the serialization feature found in C++.

Technical context
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Scopes are a fundamental piece of the UbuntuTouch user experience. Each scope offers user driven way to interact with one of more sources of either local or remote data displayed in a uniform fashion from the Ubuntu Dash.

https://developer.ubuntu.com/en/scopes/guides/scopes-guide/

The Unity Scopes API allows developers to create scopes in C++.

https://developer.ubuntu.com/api/devel/ubuntu-14.10/cplusplus/unity-scopes/index.html

Unity JS scopes is a package that enables the creation of Javascript Scopes by offering bindings of the Unity Scopes API in Javascript.

In order to get started with the unity-js-scopes package, you can have a look at the README file found at the top of the package's sources:

http://bazaar.launchpad.net/~webapps/unity-js-scopes/trunk/view/head:/README.md

In the context of the API, the Location class aggregates location specific data associated with a given SearchMetadata.

https://developer.ubuntu.com/api/devel/ubuntu-14.10/cplusplus/unity-scopes/classunity_1_1scopes_1_1_location.html

https://developer.ubuntu.com/api/devel/ubuntu-14.10/cplusplus/unity-scopes/classunity_1_1scopes_1_1_search_metadata.html

The SearchMetadata is passed down to the scope search function as seen here:

http://bazaar.launchpad.net/~webapps/unity-js-scopes/trunk/view/head:/examples/simple/simple.js#L109

The Location class is exposed here:

http://bazaar.launchpad.net/~webapps/unity-js-scopes/trunk/view/head:/src/bindings/src/addon.cc#L227

One might nee to create a new Location wrapper class to handle the new serialize function.

Deliverable
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Add support for Location::serialize and update the simple.js example to call the function.