Workspace Storage: Folder field in the Select dialog should be pre-filled

By default file will be downloaded in .UGENE_downloaded folder 

Scenario1: 

1. Select Assembles/reference.fa
2. Select Download button
3. Dialog "Select a folder to save the downloaded file" is opened           
    Expected: .UGENE_downloaded is pre-filled in Folder fileld
    Actual: Field is empty

Scenario2: 

1.  Create "test" directory in .UGENE_downloaded folder
2.  Download Assembles/reference.fa in "test" folder
3.  Remove "test" directory from .UGENE_downloaded folder 
4.  Select Assembles/reference.fa again and select Download button
5.  Dialog "Select a folder to save the downloaded file" is opened
       Expected: .UGENE_downloaded is pre-filled in Folder fileld
       Actual: "test" is pre-filled in the field