Do not extract messages with "error" string to the "ERROR" log entries in case of elements with external tools

Scenario:

1. Open the Workflow Designer.
2. Click the "Create element with external tool" button.
3. Select some existing tool in "Integrated external tools".
4. Follow the wizard until the "Command" page.
5. Set command:

   %UGENE_PYTHON2% -h
   

6. Finish the wizard configuration and run the workflow.
   Expected result: There are no errors in the log.
   Current result:

   [ERROR][15:34] -t : issue warnings about inconsistent tab usage (-tt: issue errors)
   [ERROR][15:34] PYTHONIOENCODING: Encoding[:errors] used for stdin/stdout/stderr.
   

The reason is that UGENE automatically catches lines with "error" string and puts this lines to the log. This behavior should be switched off completely for elements with external tools.