Demo/vs live

[TimPurdum]

Fixes and improvements while working on Demo for VS Live Chicago

• Added implicit operator from string to Effect
• GraphicsLayer properties
  • Effect
  • BlendMode
  • MinScale
  • MaxScale
  • ScreenSizePerspectiveEnabled
• Moved PersistenceEnabled from ImageryLayer, MapImageLayer, and ImageryTileLayer to Layer
• Sublayer
  • GetAllSublayers
  • SetProperty
  • SetLegendEnabled
  • SetPopupEnabled
  • SetPopupTemplate
• Fix JsonConverter for TileInfoFormat
• TileLayer
  • ApiKey
  • AllSublayers
  • Capabilities
  • Copyright
  • Effect
  • LegendEnabled
  • RefreshInterval
  • SourceJSON
  • SpatialReference
  • Sublayers
  • TileInfo
  • TileServers
• Fix for JS callbacks after disposal in MapView
• Fix for invalid properties sent to SetProperty
• Fix for concurrency issue when disposing AbortManager
• Fix for FeatureLayer in 3D scenes