more useful error messages in handcrafted.messages

[jsulmont]

https://github.com/360dialog/xorc-oam-compiler/blob/23500bc17fa27f061901600c227f3be40725b13c/src/handcrafted.messages#L49

The ORC compiler is able to generate 200+ different error messages. Handcrafted.messages is generated once from our parser.

Meaningful error messages have to be provided, so that the compiler can provides meaningful messages when failing.

Note the this is a very big task, and will probably be processed by refining iterations.

The Austin Orc compiler can be used as a reference.