Update ImageProxy code

[Alkarex]

fix #202
Note: breaking changes. Users will have to save their configuration again

[Alkarex]

Not tested.

@Frenzie You are welcome to check if you want to add some auto migration of the former way of storing user preferences (storing at user config top level was never meant to be supported).

[Frenzie]

The settings are extremely basic so that doesn't seem very necessary but then again there should probably be some kind of warning about it.

[Alkarex]

The settings are extremely basic so that doesn't seem very necessary but then again there should probably be some kind of warning about it.

I am not sure were the warnings should be given, though

[Frenzie]

The README seems to have acquired a changelog. Maybe that suffices?
https://github.com/FreshRSS/Extensions/tree/c726958f3fe474c013237c8d885a03225121933c/xExtension-ImageProxy#changelog

There is one other fairly obvious place, but presumably that would require development.

[Alkarex]

Would you be able to test that it still work as it should?

[Frenzie]

The proxy HTTP setting works, but the proxy HTTPS setting doesn't seem to.

[Alkarex]

Please try again

[Frenzie]

I don't have anything at hand to test the "proxy unspecified" setting (that should probably be changed to "Proxy unspecified scheme" or something because I had no idea what it was about anymore without looking at the code) but the rest seems to work now. 👍

[Alkarex]

Super. Let's made those changes in another PR. Anyone?