Remove get_server_field from leave_application

- Make get_holidays and get_total_leave_days global to module
- Replace get_server_field with using whitelisted function
get_total_leave_days
Credit days validation fixes
Payment tool fix: get outstanding sales orders
Merge pull request #2393 from nabinhait/fix1

Credit days and payment tool fixes
Merge pull request #2379 from nathando/develop

Remove get_server_field from leave_application
bumped to version 4.11.1
Merge branch 'develop'
Reference / Cheque date is after due date
Merge pull request #2396 from nabinhait/fix1

Reference / Cheque date is after due date