added ImageServiceIdentifyTask

added spec to test default use case
added tests for ImageMapLayer.identify() factory method
added to karma files
renamed identify tasks to IdentifyFeatures and IdentifyImage
refactored common methods of identify tasks into Idenityfy.js
image identify requires geom sent as JSON, not x,y&sr=4326
added identify image example
added tests/props for mosaicRule, renderingRule, pixelSize
added api ref page for L.esri.Tasks.IdentifyImage
added ability to un/bind popups for image map layers

refactored most of popup related functions to RasterLayer
added support for returnCatalogItems

added method to set taks param
added code to convert catalog features into a GeoJSON feature set
added tests for w/ and w/o geometry
documented new methods on api reference page
update the API ref page w/ bindPopup() and related methods

also sets identify task mosaic rule if the the image service mosaic rule is set
added an image map layer custom popup example page

based on the dynamic map layer custom pop up page
Merge pull request #325 from tomwayson/issue-296

Image service identify