Improve onboarding in the GT Book

[onierstrasz]

Although there is a lot of material in the GT Book to help newcomers get started, many experience difficulties in learning how to use GT effectively. The issue is to improve the onboarding experience by adding some new material, and providing better roadmaps to the existing material.

Steps:

• Start with a page introducing GT and moldable development (more like a blog rather than a slideshow)
• Emphasize GT as a case study itself in moldable development
• Next emphasize learning how to learn (what are the basic skills you need to learn?)
• Explain how to search and how to work with the inspector
• Next learn how to make contextual extensions
• Provide a detailed roadmap through typical use cases for moldable development

Some possible use cases:

• Creating a knowledge base
• Exploring an API
• Analyzing data
• Modeling a domain
• Visualizing code
• Implementing a language