Separate download and upload queues

[Brandon B.]

Problem:
My use of the FileZilla client frequently consists of downloading several large files and uploading a few small files in return. Most generally the file to be uploaded is time sensitive and must occur as soon as possible.

With the current queue process as it is now and the number of simultaneous file transfers is set to a limited amount; in order to upload an unspecified amount of fiels while downloading the maximum transferable limit of files or more, I must do the following:

1. Set the priority the the upload files higher than the download files. (Not always possible)
2. Increase the transfer queue by the amount of files that I need to upload. (This can be an inconvenience because I have to go count all of the files to be uploaded)
3. Once all upload file transfers have started the transfer process, I must go and revert the concurrent transfer limit to the previous value before any of the upload transfers are finished so as to not start another download transfer. (At times the uploaded files can be very small in size and that can make this step nearly impossible.)

Proposed solution:
Have an option in the settings dialog that will support the ability to have separate upload and download queues and speed/count transfer limits for both.

Justification:
Majority of, if not all, internet connections allow for data to be both uploaded and downloaded concurrently. I have not heard of an FTP protocol nor an ftp server side implementation that cannot handle simultaneous upload and download of data. (I'm nearly positive that the FTP protocol must talk both ways in order to function properly). Therefore upload and download transfers should be treated as separate entities as they can be operated simultaneously.

Restrictions to proposed solution:
There may be a limit of concurrent connections that can be established per single user credentials to a specific FTP server. If this is the case, then it will be the user's responsibility set the transfer limits accordingly.

System details:
FileZilla Client version: 3.5.3
OS: Windows Server 2008R2 SP1 (VM on top of ESXi 4.1)

[Slawa]

Duplicate of ​https://trac.filezilla-project.org/ticket/4938