Add support for optional metainfo fields in Create New Torrent panel

[Reportage]

Since the support for optional metainfo is already in the code, and is displayed when torrents have been generated by 3rd party clients (and enabled), adding the option to embed a comment and the creation date when creating a torrent would be helpful.

To add a comment, an additional text field under the create torrent field; to embed the creation date, an option in the configuration section.

[zzz]

Creation date is already stored, and displayed, for locally-created torrents.
Comment field is doable, but worth the added complexity in the create torrent form? I don't think so but don't feel that strongly about it.

[Reportage]

Mockup of comment field

[Reportage]

The attached image indicates a mockup of a simple, unfussy implementation of the UI for adding an embedded comment to the torrent. For most purposes, it should be big enough, otherwise, cutting and pasting a larger comment should keep most happy.

For the tooltip, something along the lines of "Add an optional comment or description to be embedded in the torrent file".

[Reportage]

The metadata section on ​http://torrenteditor.com might serve as a useful template for adding metadata to snark torrents. In addition to adding a comment, the 'Created on' (with the option to toggle off) and 'Created by' fields could be useful.

[Reportage]

Meta data edit section on ​http://torrenteditor.com