UI to display flash usage and file sizes

[maks]

It would be very helpful to show users how much flash storage is remaining. This is really only useful during sample import, so displaying this only on the import screen makes most sense.

Also it's not useful to know remaining space without also seeing the size of each sample listed in the import sample screen so need to add file size display for samples too.

What I'm not sure about UX and performance wise is if we should show sizes along side filenames or what is my preference: show file size of a sample file separately (eg. on a bottom "status" line) only when it's highlighted.