Tutorial 3: Structuration and branching - init (#9)

* Init from MarekSuchanek/FPCourse

* Basic branching improvements

* Guards order, named patterns

* Evaluation, wildcards and syntactic sugar

* Information about term bottom

* Bang patterns

* Further reading links added

* Grammar fix with Grammarly

* Lazy pattern matching

* corrections and simplifications

* comment removed

* Fixing typos and examples

Author: MarekSuchanek