#12 Use the consistent labels throughout the program

[Dzmitry]

I believe the following deviations should be consolidated and the same wording should be used everywhere in the program:
- Down speed (data) // column set-up right-click menu; both torrents table and peers table
- Download speed (payload) // Preferences > Status bar
- Download payload speed // Details panel

The same concerns Upload.

And also compare (all in the same columns set-up popup menu):
- Download
- Down data
vs
- Down speed
- Down speed (data)

'ETA' column value should probably be named the same in 'Details' panel, not 'Time left'