added support for UIActivityIndicatorView while the image is
downloaded, without adding extra ‘setImageWithUrl’ methods to the
UIImageView+WebCache category.
I used [this pull
request](https://github.com/mythodeia/UIActivityIndicator-for-SDWebImage
), original author is [JJSaccolo](https://github.com/JJSaccolo), and
modded it a bit to support loading indicator while the image is
downloading.
the usage is basically this right before the usual sd_setImage...
methods:
```
// show activity indicator
[cell.imageView setShowActivityIndicatorView:YES];
// choose indicator style
[cell.imageView
setIndicatorStyle:UIActivityIndicatorViewStyleGray];
```
- added `username` and `password` properties on `SDWebImageDownloader`
- added `shouldUseCredentialStorage` and `credential` properties on `SDWebImageDownloaderOperation`
- `SDWebImageDownloaderOperation` conforms to `NSURLConnectionDataDelegate` (it used to implement the methods, but didn't stated the protocol in the declaration)
- removed deprecated methods: `- connection:canAuthenticateAgainstProtectionSpace:` and `- connection:didReceiveAuthenticationChallenge:` with `- connectionShouldUseCredentialStorage:` and `- connection:willSendRequestForAuthenticationChallenge:`
- updated demo project to download one image the requires HTTP auth