Streamline printk statements and switch to pretty-printk

[tpiekarski]

Streamline printk and switch to pretty-printk

Streamline all printk statements in form and usage of severity and switch over to pretty-printk which was already integrated by issue #51.

[tpiekarski]

Consider to use pr_fmt like it is done in the Linux Kernel Sources and pointed out by KamilCuk. Makes pretty-printk rather obsolete.