Revert "Starting problem 19."

This reverts commit 4c8e0a69959df690c728c772f4c683b1fd2bb4d1.
Revert "Revert "Starting problem 19.""

This reverts commit 479bec7cf9e28c728a5d196e23f67676332d43c4.
Revert "Revert "Revert "Starting problem 19."""

This reverts commit 5519e718d2e7890a29538abb0f8c2a2ea080aac5.
Revert "***** IN PROGRESS *****"

This reverts commit c52bd1649be964b5aace251577de416f1a24b4b9.
Revert "Contains txt files with data to read in for selected problems."

This reverts commit af576703d5eb8b8f1d814144272d01d34d23c5dc.
Factorial digit sum

648
***** IN PROGRESS *****
***** IN PROGRESS *****
Txt file to be read in to problem 18.