For each of these TODOs:
- If there's an active bug tracking the work, and the TODO provides
something of value, I left it and standardized the formatting. I also
added comments to the bug.
- If the comment provided no value (implement feature X when we do feature
X), I deleted it with impunity.
- If the comment was stale (won't fix or just out of date), then we
removed it uncerimoniously.
There was a single TODO that was actually actionable, so I enabled that
test.
- add missing `[NotNull]` attributes
- remove now-unneeded usings for ...ModelBinding.Internal namespace
Also get ModelBinding test project working under CoreCLR
- create separate k10 and net45 folders under test in VS
- add `[InternalsVisibleTo]` to make `TypeExtensions` visible to test assembly
- correct tests' `CultureInfo` use to compile under CoreCLR
- ifdef out CoreCLR tests depending on Moq, ReadOnly, ...
- remove a couple of tests expecting TypeConverter to work