add number of elements to variable axis description

[gdkrmr]

Currently:

Data Cube view with the following dimensions
Lon                 Axis with 1440 Elements from -179.875 to 179.875
Lat                 Axis with 720 Elements from 89.875 to -89.875
Time                Axis with 1702 Elements from 1980-01-01 to 2016-12-26
Variable            Axis with elements: bare_soil_evaporation black_sky_albedo .. transpiration white_sky_albedo 
Total size: 147.91 GB

better:

Data Cube view with the following dimensions
Lon                 Axis with 1440 Elements from -179.875 to 179.875
Lat                 Axis with 720 Elements from 89.875 to -89.875
Time                Axis with 1702 Elements from 1980-01-01 to 2016-12-26
Variable            Axis with 18 elements: bare_soil_evaporation black_sky_albedo .. transpiration white_sky_albedo 
Total size: 147.91 GB