Add bitcomet to Download Management Tools

[zayzou]

NOTE: Each discrete (stand-alone) request should be in its own issue.

Put "Add ____" as Title
[ ] Done

Provide a link to the proposed addition.
Place link here.

Explain why it should be added
BitComet is a free C++ BitTorrent Download Client
BitComet is powerful, super-fast and easy-to-use.

Additional context

• Fast and Powerful
• Long-Term Seeding
• Intelligent Disk Caching
• Preview while Downloading

Issue Checklist

Put an x in the boxes once you've completed each step. You can also fill these out after creating the issue. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before responding to the issue.

• I have checked for other similar issues
• I have explained why this change is important
• I have added necessary documentation (if appropriate)