Images will be loaded from an external source (e.g. http://example.com/img.png) only if the reader is explicitly set to allow it via `$reader->setAllowExternalImages(true)`.
* All Readers - Allow or Forbid Fetching of External Images Release210
Add to all readers the option to allow or forbid fetching external images. This is unconditionally allowed now. The default will be set to "allow", so no code changes are necessary. However, we are giving consideration to changing the default.
* Update Changelog
oleibman
