Modified directory structure to use Soomla from UnityScript code

I took the liberty to move the 'Soomla/Assets/Soomla/Scripts' folder and its content to 'Soomla/Assets/Soomla/Plugins/Soomla/Scripts' to prioritize the C# scripts compilation so the API can be used from UnityScript code. This doesn't change any existing functionality and maintains compatibility with any project using Soomla in its current form.

This is something I did at work in order to reach the Soomla API from our UnityScript codebase, I repackaged Soomla internally and I thought that other developers might be interested by this slightly altered directory structure.

This pull request was redone at the request of @rafaelos since the structure of the project changed with the latest version. I retested it and didn't notice any change, everything works exactly like before with the new directory structure.

The previous pull request can be found [here](https://github.com/soomla/unity3d-store/pull/195).