Remove "ItemSQLs" from unit configs

There are 2 (among many) settings in unit config called:

• ListSQLs
• ItemSQLs

These are respectively database queries to select a list of items (on grid template) and one item from a list (on editing template).
Both database queries are usually the same and that's why there is a fallback, which tells that when ItemSQLs setting is missing, then ListSQLs setting is used instead.

This is very good, but since we still have both ItemSQLs and ListSQLs present in most of unit configs, then replacing one database query will required twice same amount of PHP code because we need to change both settings.