Second week lectures added.

Anonymouse functions, passing functions as arguments/parameters.
Products and sums functions (non-tail recursive, tail recursive, with
functions as parameters/arguments, with anonymouse functions as
parameters etc...)
Newtons square root method revisited.
Revert "Second week lectures added."

This reverts commit 3481a234910bd2d2e86d21cb6155a6a755db3c28.