Support of column names in index definition

Allow long with field_no pass field_name for index creation
(alteration) routines.

Add new method of defining indexes:
 - parts = { {field = field_name1, type = field_type}, {field = field_name2, type = field_type}, ...}
 - parts = { {field_name1, field_type}, {field_name2, field_type}, ...}
 - parts = { {field_name1}, {field_name2}, ...}
 - parts = {field_name1, field_name2}
 - parts = {field_id, field_id}

Fix 2814