Make it easier to add tags

[C0080900]

I understand that I can right click images and edit the ITPC data.

But it'd be simpler to add a context menu, or sidebar similar to Picasa's that allows us to tag our images easily.

Another thing would be user copies/pastes tags from like a .txt file, XnView should treat them as seperate tags if the tags have commas.

Just my feedback.