Merge pull request #188 from corliss/dev3

ModalWindow and DataStoreView+GridViewSelection changes. NUnit based unit tests.
Update README.md
Revert "Graphics: Make MeasureString virtual for testability."

This reverts commit f80b8052fe07c7b2732060225fae26d28e1b2c6b.
Revert "Refactor interface IMeasureString."

This reverts commit 13a48960b5fbd089efe5f4fc5dce6b20b6d3060a.
Tutorials now execute post build action via xbuild on os x & linux
WPF: When running an application without a form, application must be shut down explicitly
Update tutorials for new menu/toolbar api's
Nuget should use base directory specified by project file (e.g. when used from Eto.Test.* projects, which are at a different level than other project files)
WinForms: Fix autosizing a form with a single control such as Drawable, etc.
Fix comments
Refactor UnitTests to their own assembly
- Add unit test runner in Eto.Test instead of using custom runner
- Allow using an actual generator when running via nunit gui, configured through app.config
- Ensure tests are invoked so they are executed on the main thread
- Remove need for platform-specific unit tests as all tests can run on any platform
Make ToolTip/Image/Shortcut non-virtual.  If setting these values in a constructor, then the behaviour is undefined.
Remove csproj noise from latest Xamarin Studio
Update Mobile projects for latest api and unit tests
Mac: Fix validation for system command mapping
Mac: Fix toolbar tint logic, NSColor.ToCG() extension did not work in certain cases. Refactor to use new core image helpers
Mac: Fix setting MenuItem/ToolItem.ToolTip to null
ToolItem/MenuItem fixes
- Properly order toolbar items when inserted.
- Set enabled properly when created
- Set ToolItem.ID from Command.ID
Code cleanup
Direct2D: Throw exception instead of burying it for Image.GetPixel
Remove NUnit namespace mappings.