fix issue #3: crash when running an unknown program

check if a message should be printed to the main vga screen by checking if any syscall in the 'syscall stack' is the foreground process

route the shell service to the vga output

rewrite general IO using an IO-manager

use string identifiers for events ...

(some rework of the string saving system was required)

use stringmap for communication between processes

mov syscall handlers to different files

enable freeing of memory

read the initrd file to get the memory location of the first userspace program

find the initrd in the multiboot 2 information structure