UC-152 Avatars cannot be uploaded on some wikias

There were 2 problems here:

First, in aim.js, the code was interpreting a response from the server from UserProfilePage::onSubmitUsersAvatar as html, when it's actually json. This was HTML escaping ampersands into ```&amp;```. Using textContent to get the raw value fixes that.

Second, The upload error presents itself on foreign language wikias which are using vignette. This is because vignette appends ```path-prefix=<lang>``` to the end of thumbnails on foreign language wikias and we were manually constructing a query string using that thumbnail to be sent to the server. Letting jquery construct that query string fixes that.
This is mostly whitespace and coding convention changes, and removing wfProfile calls. There are 2 places where I changed some of the logic, here's one.