Initial OpenAPI prototype from first working session

Created by: tedepstein

This commit has the prototype from our first working session. It includes:

• The core OpenAPI specification document in /models
• Sample of generated server stubs, client libraries and documentation formats in the /gentargets subfolders
• Project and build files for Eclipse with RepreZen API Studio.

I also added some updates to the README with a brief introduction and some information on the development environment. Trying to be helpful to community members who want to contribute, without being opportunistic. Please review and feel free to suggest changes.