Upgrade requests version to 1.1.0

Reasons:

* Starting from 1.0.0, requests will have a stable API which didn't have up until now, also it included several fixes and enhancements
* requests requirement was added after 1.8 so it shouldn't break any applications built on the latest stable release
* The new spatial harvesters require this newer version, keeping an older one in core will cause a lot of pain

The only supported extensions that I know to be using requests are:
* resource_preview (core)
* datastorer
* archiver

For all of those I've done the necessary changes and updates, which will get pushed if this gets merged to master