Prior to this commit, measurements to be collected were specified via
"sites" and "kinds" parameters. This has the limitation that if you
wanted measurments of kind X from site A and kind Y from site B, you'd
have to specify them as
reset(sites=['A', 'B'], kinds=['X', 'Y'])
Which would have the effect of also collecting measurments Y for site A
and measurments X for site B. This commit adds the option of specifying
individual channels, via thier labels, e.g.
reset(channels=['A_X', 'B_Y'])
so that only the channels you're interested in will be collected.
