Updates to Readmes (#544)

Updates to readmes as per common designs

Author: jenmerritt

feature_layers/feature-layer-selection/README.md

@@ -19,16 +19,16 @@ Click on a feature in the map. All features within a given tolerance (in pixels)
 3. Identify nearby features at the clicked location using `identifyLayerAsync(featureLayer, clickLocation, tolerance, returnPopupsOnly, maxResults)` on the map view. 
 4. Select all identified features in the feature layer with `selectFeatures(features)`.
 
-## About the data
-
-This sample uses the [Gross Domestic Product, 1960-2016](https://www.arcgis.com/home/item.html?id=0c4b6b70a56b40b08c5b0420c570a6ac) feature service. Only the 2016 GDP values are shown.
-
 ## Relevant API
 
 * Feature
 * FeatureLayer
 * ServiceFeatureTable
 
+## About the data
+
+This sample uses the [Gross Domestic Product, 1960-2016](https://www.arcgis.com/home/item.html?id=0c4b6b70a56b40b08c5b0420c570a6ac) feature service. Only the 2016 GDP values are shown.
+
 ## Tags
 
 features, layers, select, selection, tolerance

feature_layers/feature-layer-shapefile/README.md

@@ -10,7 +10,7 @@ Shapefiles store location, shape and attributes of geospatial vector data. Shape
 
 ## How to use the sample
 
-When the sample starts, a feature layer from a shapefile is added to the map. Pan and zoom to inspect the feature layer.
+Pan and zoom around the map. View the data loaded from the shapefile.
 
 ## How it works
 

geometry/list-transformations-by-suitability/README.md

@@ -27,6 +27,10 @@ If the selected transformation is not usable (has missing grid files) then an er
 * GeometryEngine
 * TransformationCatalog
 
+## Additional information
+
+`DatumTransformation` has two subclasses, `GeographicTransformation` and `HorizontalVerticalTransformation`. `GeographicTransformation` is used to transform coordinates of geometries between spatial references that have two different geographic coordinate systems. `HorizontalVerticalTransformation` is used to transform coordinates of z-aware geometries between spatial references that have different geographic and/or vertical coordinate systems.
+
 ## About the data
 
 The map starts out zoomed into the grounds of the Royal Observatory, Greenwich. The initial point is in the [British National Grid](https://epsg.io/27700) spatial reference, which was created by the United Kingdom Ordnance Survey. The spatial reference after projection is in [web mercator](https://epsg.io/3857).

portal/token-authentication/README.md

@@ -34,7 +34,11 @@ Once you launch the sample, you will be challenged for an ArcGIS Online login to
 
 ## About the data
 
-The Traffic web map uses public layers as well as the world traffic (premium content) layer. The world traffic service presents historical and near real-time traffic information for different regions in the world. The data is updated every 5 minutes. This map service requires an ArcGIS Online organizational subscription.
+The [Traffic web map](https://arcgisruntime.maps.arcgis.com/home/item.html?id=e5039444ef3c48b8a8fdc9227f9be7c1) uses public layers as well as the world traffic (premium content) layer. The world traffic service presents historical and near real-time traffic information for different regions in the world. The data is updated every 5 minutes. This map service requires an ArcGIS Online organizational subscription.
+
+## Additional information
+
+Please note: the username and password are case sensitive for token-based authentication. If the user doesn't have permission to access all the content within the portal item, partial or no content will be returned.
 
 ## Tags