Reorganize architecture specific features

[d4ilyrun]

What

I tried to split the generic functions and the architecture specific ones, but i failed

Most of what's been done inside the kernel currently is architecture specific, but some of it is still present inside the kernel/src folder anyways. I should clean this up a bit, to make it more accurate, or maybe completely get rid of this architecture altogether ....

Interfaces

Maybe this change would also be a good time to take a look at the existing interfaces (timer, ...), and see if they could be improved or if they depend on architecture specific constraints.

Misplaced features

• PIT: only available inside intel's chips
• PIC: only available inside intel's chips
• UART: implementation is arch specific
• Timer: arbitrary frequency constraint (inherited from the PIT => should go inside the PIT functions)
• crt0.S: contains assembly code
• kernel/src/asm: counter-intuitive to have assembly code inside the generic sources
• interrupts.h: find a way to automatically import this file

[d4ilyrun]

Closed with ab150c4