Solutions to 1-13, except for 4.

I overwrote 4 by accident.
#14 solved
Use 64-bit ints explicitly.

Allows problem 14 to still work on 32-bit platforms, even though the
resulting code is significantly slower.
Create problem 15.
Problems 16-18.
Add problem 19
Add problem 20
Add some more solutions.
Problem 22
Move Primes into it's own module.
Problem 23
Problem 24
Problem 25
Problems 26, 27
Problem 28
Problem 29
Problem 30
Problem 31
Problem 32
Math instead of 'read'.

Manipulating Ints and performing the direct math rather than
building strings and using 'read' to parse them as numbers, gives
about a 100-fold performance improvement.