Added m and length to Heap.
Basic implementation of FreeLists with an array that stores the positions of the start of the free lists.
The free lists are singly linked lists inside the heap.
BuddySystem: Separated implementation from header.
BuddySystem gets a pointer to the heap in the constructor.
It creates its own FreeLists object.
Fixed initialisation of the BuddySystem and Heap in the main.cpp.