Issue 1603, rewrote first sentence - uses the php curl lib

Issue 1603, rewrote first sentence - uses the php curl library, enabling connections to remote web services
Merge pull request #2969 from mrsmuneton/3.1

Issue 1603, rewrote first sentence - uses the php curl lib
FIX Fixes silverstripe/silverstripe-cms#947 GridField sorting.

- Ensures magnifying icon only shows when required.
- Related to: silverstripe/silverstripe-cms#810 (@chillu comment).
- Also fixes #1492.
- Includes Behat tests.