Add system variable so that import with "Replace Existing Data" will really replace existing data

Version: 2019

Type: Features

Category: Data Handling

Subcategory: Import Data

Jira: ORG-18790

Added a system variable @IRE for import Excel file with "Replace Existing Data" Import Mode.

@IRE = 1(default): Replace the existing sheets in the active Workbook from the active sheet on.

@IRE = 0: Only replace the active sheet, and create new sheets to import following Excel sheets.