Improve message when a test fails

[laurent-thiebaud-gisaia]

Currently when 2 columns aren't equal, we have to compare each column on the same line; with many columns it is very hard. There we add a csv-formatted message that can be past into eg. excel and displays each row under the other, in order to ease the comparison.

[laurent-thiebaud-gisaia]

Example of added message:

To be pasted into a CSV parser for debug
'result',arlas_track_timestamp_end','arlas_track_timestamp_start','id','seq_id' 
'','10','1','id1','id1#1_100' 
 '#','10','1','id1','id1#1_100s'

'','20','10','id1','id1#1_100' 
 '=','20','10','id1','id1#1_100'

'','50','20','id1','id1#1_100' 
 '=','50','20','id1','id1#1_100'

'','100','50','id1','id1#1_100' 
 '=','100','50','id1','id1#1_100'

'','1000','100','id1','id1#100_2000' 
 '=','1000','100','id1','id1#100_2000'

'','2000','1000','id1','id1#100_2000' 
 '=','2000','1000','id1','id1#100_2000'

'','10001','10000','id2','id2#10000_10001' 
 '=','10001','10000','id2','id2#10000_10001'

[laurent-thiebaud-gisaia]

It once saved my day...