GetCropUrl - Removing duplicate code
GetCropUrl - ensuring that GetCropUrl(width,height) works and also adding the useFocalPoint parameter
Removing HasPropertyAndValueAndCrop method as it's no longer needed
GetCropUrl - further code duplication removal and 2 new unit tests
GetCropUrl - Stylecop and an additional test
ImageCropDataSet - a little bit of Stylecop
GetCropUrl - moved propertyAlias and cropAlias to after width and height so that GetCropUrl(100,100,"myProperty") is possible and renamed useFocalPoint to preferFocalPoint
Fixing the CacheBusting on GetCropUrl as it was totally random which meant the server cache was creating a new cache file for every request.  Now changed it to use item updateDate.ToFileTimeUtc as the cache busting value so it will change only when the item is updated in Umbraco.
Merge pull request #330 from Jeavon/7.1.0-ImageCropper-JeavonWIP

7.1.0 image cropper - removal of lots of duplicated code, fixes for various param options and some further unit tests