Kernel: Rename MMU to PageTable

This is more descriptive name for what it actually represents

kernel/kernel/Scheduler.cpp

@@ -185,11 +185,11 @@ namespace Kernel
 
 		if (current.has_process())
 		{
-			current.process().mmu().load();
+			current.process().page_table().load();
 			GDT::set_tss_stack(current.interrupt_stack_base() + current.interrupt_stack_size());
 		}
 		else
-			MMU::kernel().load();
+			PageTable::kernel().load();
 
 		switch (current.state())
 		{