Updated error handeling

Now the subfolder structure is supported.
Max number of cards is set to the right subfolder.
Added unique random number generatot
Merge branch 'Sample_files' into develop

Conflicts:
	Pictures/txt/1/1.txt
	Pictures/txt/1/2.txt
	Pictures/txt/1/3.txt
	Pictures/txt/1/4.txt
	include/memory.h
	main.cpp
	src/memory.cpp
Finished "set_cards" function

Cards are selected out of all available files in the given folder randomly.