Lexical table, XLSX export/import

Be able to import and export Lexical table from XLSX files

Validation test

1. Create a Lexical table
2. export it with the xlsx format
3. remove all lines except 3-4
4. import previous data from the xlsx file -> no need to re-open the lexical table and the lines are restored
5. Create a new table from the exported xlsx table
6. the table is shown