Fix loadcsv

This commit fix 2 bugs on loadcsv:

• how csv is loaded and how first line is ignored. Now the number of cols is calculated based on second line, not on first. So a file with empty header will work correctly.
• problem with files with 1 row, on this case loadcsv try to access a inexistent position from _values and then a segfault is generated closing the IOC.

@thomasfay please review this MR first it corrects a bug and is better to be merged before the others.