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
- Removed unnecessary and inconsistent parentheses
- Made the `Price` property a `decimal` instead of `float` (come on, `decimal` is used for monetary values for a good reason)
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