Migrate more content from DevGuide 3.0

[jgadsden]

Describe what change you would like :
There is a lot of good content in DevGuide 3.x that has not yet been migrated to version 4.x
It would be good to get more of this content into 4.x

Context :
Section: various

An example raised by @sydseter is the section on Memory:
https://github.com/OWASP/DevGuide/blob/3.0-final/03-Build/0x14-Memory.md

[sydseter]

Yes, it's a pity to lose this. Let's start a new branch!