Build the exercises

Builds the exercises and moves their files into the respective folders

build_exercises(exercises_home = "./content/exercises/", build_all = FALSE)

Arguments

exercises_home	Character; path to the exercises folder
build_all	Logical; defines whether all exercises are built or only those that have been modified. Relies on a CSV file containing checksums that is created the first time build_sesssion() was used; default is FALSE