[MEMORY/DISK] Combined graph

[VA1DER]

I would like to see the memory graph done as a united graph. One graph with multiple colours for free, used, buffers, and cache.

This is a better, more united way to show it. Having multiple graphs with data that is mutually dependent makes it harder to visualize.

Like this:

I would also like to see all capacity graphs (used/free) as combined graphs where used and free are separate colours. Green vs red is a good combo. Again, this is a better visual representation.