Add material for type-directed programming

See merge request lamp/cs-210-functional-programming-2019!11

Fixes to progfun1-week4

See merge request lamp/cs-210-functional-programming-2019!9

- Remove type incorrect hint for uncurry2 (I don't think this hint helps understanding the question...)
- Rename f' to g in the curry2 description (someone asked why we are taking the derivative of f...)
- Swap the arguments of curry2/uncurry2, `(Double, Int)` is more convinient to give an example with `Math.pow`

Fix typos

See merge request lamp/cs-210-functional-programming-2019!7

# Conflicts:
#	slides/sources/progfun1-2-3.md
#	slides/sources/progfun1-2-5.md
#	slides/sources/progfun1-2-6.md
#	slides/sources/progfun1-2-7.md
#	slides/sources/progfun1-3-1.md
#	slides/sources/progfun1-3-2.md
#	slides/sources/progfun1-3-3.md
#	slides/sources/progfun1-3-4.md
#	slides/sources/progfun1-3-5.md
#	slides/sources/progfun1-4-1.md
#	slides/sources/progfun1-4-2.md
#	slides/sources/progfun1-4-3.md
#	slides/sources/progfun1-4-4.md
#	slides/sources/progfun1-4-5-decomposition.md
#	slides/sources/progfun1-4-5.md
#	slides/sources/progfun1-4-6-pattern-matching.md
#	slides/sources/progfun1-4-6.md