Drags element identified with locator.

Element can be moved either by a certain amount of pixels with movement argument, or on top of another element with target argument.

target is a locator of the element where the dragged object is dropped.

*Examples:*
| Drag And Drop | myElem | +50 -35 | # Move myElem 50px right and 35px down. |
| Drag And Drop | elem1 |target=elem2 | # Move elem1 over elem2. |