Merge pull request #191 from corliss/dev3

Test fixes and new tests
Fix publishing nuget packages, add batch files to execute msbuild more easily
Mac: setting CheckBox.Checked to null when not using ThreeState mode should set check to false, not true
Mac: Exclude invisible controls from preferred size calculations
Obsolete code removal: Colors
Remove obsolete code: Key enumeration.
Remove obsolete code: Graphics methods.
Remove obsolete code from: Bitmap, ColorCMYK, ColorHSB, ColorHSL, Font, FontFamily, PixelLayout, TableLayout, ButtonMenuItem.
Remove obsolete code from: DockLayout, DynamicLayout, ToolItem
Remove obsolete code from: Icon, IndexedBitmap, Palette, Point, PointF, EtoEnvironment.
Remove obsolete code from: Forms/Actions folder, Application.cs, Control.cs.
Remove obsolete code from: Control.cs, Drawable.cs, GridItem.cs, KeyEventArgs.cs, Platform.cs, Resources.cs, Style.cs.
Remove obsolete code from: Navigation, Panel, Splitter, TreeView, Layout, ButtonMenuItem, ContextMenu, MenuBar, Range, Window, Generator.