Add support for uploading files linked to on a page, using the context menu

[PurgingPanda]

#513

Very simple addition so you can upload files that are linked to on a page. For example pdf files so you do not have to download them and manually upload them.

A current problem I noticed is that when trying to upload links directly from google search results it opens a print dialog. This seems be fixed when using an extension that removes google redirect links. https://addons.mozilla.org/en-US/firefox/addon/google-no-tracking-url/?src=search

[lidel]

Thank you! 👍

This is a good feature and works really well on links to big images but I was worried about user doing this on a link to a file where name matters or is a HTML page, so I tweaked it a a bit :)

UX problem

Executing on a link to other page will fetch HTML, upload it to IPFS and then open it in a new tab, and as it is HTML, it will render the webpage, often broken due to changes in Images/CSS/JS paths. Not a great experience when you miss-click.

Potential Solution

We don't want to remove options, so let's give users more choice!
As a drive by commit added to this PR added a second option that lets users choose if filename of uploaded link should be persisted. I believe it makes a lot sense for things like PDF, ZIP, or even images. I also changed language to match one from ipfs/ipfs-gui#35:

Test via context menu on this link:

https://upload.wikimedia.org/wikipedia/commons/thumb/c/cf/Doma%C5%BElice%2C_Jir%C3%A1skova_43_(9102).jpg/320px-Doma%C5%BElice%2C_Jir%C3%A1skova_43_(9102).jpg?foo=bar#buzz