mk_individual table: replace field name to be more inforamtive and correct

[GalAvineri]

The table mk_individual contains two fields named 'mk_individual_name' and 'mk_individual_name_eng'.
These fields actually contain only the last name of the knesset memebrs, and not their full name.

So perhaps in correspondace to the fields 'mk_individual_first_name' and ''mk_individual_first_name_eng', the new field names 'mk_individual_last_name', 'mk_individual_last_name_eng' would be better