xhci: refactor and seperate out commands

fix issue #3: crash when running an unknown program

xhci: clean up slot initialization

fix weird problems with getPhysicalAddress system call

fix issue with printing where the first message would not get printed

create async xhci command function using events

trigger interrupts from xhci controller

fix problem where page fault happens because not the whole string is mapped in a insertString system call

refactor syscall.c

add sleep function to PIT driver

receive xhci events

fix issue #1: ELF files not loaded correctly

add system call to retrieve the physical location of a virutal address

print basic XHCI information

add lspci user programm

move 'gets'-functionality to ioManager to simplify the shell source code

add await syscall

start the program name entered in the shell

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

free the system call structure of a crashed system call process

add system call to look up the names of functions

add basic stack tracing ability

notify other tasks of a exception happening ...

subscribe to the interrupt 0 to be notified about exceptions

gracefully handle crashes of a user mode programm

fix interrupts occuring while in user mode

rename service proivder to service function ...

now matches the documentation in the wiki

free stack of unused system call processes ...

saves about 1/2 of previously used memory

add kernel events ...

kernel events get triggered by the kernel when certain things happen.
first example: log a message whenever a new programm is loaded from the initrd