Get validation sample working
- add files needed to complete the sample
- implement rc2 (and later) `IClientModelValidator` interface
- remove validation TODOs; implement them for real
- remove unused `Movie` properties
- remove and sort `using`s
- adjust `validation.rst` to match new sample
- correct a couple of small typos
- use sample files instead of code blocks where possible
- addresses the remaining bits of #1154
fix link
minor fixes
fix link
code formatting
consolidate sample files
formatting fix
modifications after feedback
changes after feedback
changes after feedback
edits
edits
edits
edits
changes
Doug Bunting
RachelAppel