Update the specification to include Quick Look rules

This merge request consists of:

• Expression syntax à la Quick Look
• GADT and Case typing rules illustrated in Quick Look figure 10
• Explanation for the App rule
• Build instructions in the README
• Quick Look bibtex
• VDQ-t2t rule from proposal 0281; extended with Constraint support

Things that will be added later:

• Explanation for all the other "sophisticated" rules
• Lhs2Tex support and examples
• Declaration judgements and rules