Tutorial ext: Improve task/solution handling.
css: Add styles for task stuff.
Add some tasks + minor improvements.
Update tasks, add solutions.
Grammar: it's vs. its.
Add chapter on functions.
Add glossary and correct line endings in index.
Correct indentation in cpp files (2 -> 4 spaces).
Use http instead of https for hyperlinks.
Logic: Add the ternary operator.
Begin chapter on user types (empty).
Types and vars: Initialization vs. assignment.
Minor changes.