Force local cache update when user changes their profile picture

Created by: Treer

Fixes issue #344 (closed), so avatar changes appear to work immediately.

The short summary is that javascript in force_image_reload.tpl creates an iframe containing the avatar image, then invokes location.reload(true) on the iframe contents, forcing the browser to re-fetch the image. It's an implementation of method 4, here, which is convoluted, but the javascript is only ever added to a page when the user changes their profile picture.

Updating immediately on the user's browser was on my wishlist because it's one of the first impressions new users have of Hubzilla, I don't want to be trying explaining to them that sure, it works on facebook but facebook isn't decentralized. Plus it's not like anybody else on the network will already have the new person's avatar cached.

I haven't removed the system notice that suggests the user "shift-reload".

There's also a minor commit in there that adds "requires" asterisks to the "Create Channel" page.