Add start position information for a drag event

[kitsonk]

Type: feature

The following has been addressed in the PR:

• There is a related issue
• All code matches the style guide
• Unit or Functional tests are included in the PR

Description:

This PR enhances the Drag meta provider by providing a start property on drag results. This start property is a matrix of positional information from the pointer event. It therefore makes it possible to determine where the pointer location is by taking one of the properties of the start property and adding the delta property.

This is useful in cases where a render function needs to instantiate something at a particular location of where the pointer event is occurring.

Resolves #715

[kitsonk]

I removed a redundant if block, the other uncovered else block should ideally have a test where there is a RAF before the up event which should cause the start to be populated.

[tomdye]

Looks like this should work fine for JLG's needs. Thanks for the quick turnaround.