Publish documentation about building and installing process

Dear developers,
do you have any plans to publish in Github clean and full documentation about building and installing process of libva?
Current documentation is extremely minimally.

I am from [infrastructure](https://github.com/Intel-Media-SDK/infrastructure) of MediaSDK as you know one of our dependencies is libva. We have to have full documentation about how to build, install and configure all our dependencies for our customers. We may help you with documentation and send it for approval as Pull Request.