Merge branch 'jeffs.euler11'

Implement upward_diagonal_products for Euler 11

Implement downward_diagonal_products for Euler 11

Implement vertical_products for Euler 11

Implement horizontal_products for Euler 11

Replace hand-rolled math with slice::windows

Derive Default to make clippy happy

Replace loops and mutation with fluent call chain

Use prime_sieve in euler10 for performance

Add prime_sieve function

Rename a parameter for clarity

Rename functions for consistency

Ignore slow test by default

Solve problem 10

Move prime number generation to lib crate