- #2705
- add `JQueryFormValueProvider` and `JQueryFormValueProviderFactory`
- carry some code forward from MVC 5; correct to follow current coding guidelines
- refactor `ReadableStringCollectionValueProviderTest` into abstract `EnumerableValueProviderTest`
- enables reuse in new `JQueryFormValueProviderTest`
- also run these tests in `CompositeValueProviderTest`
nits:
- do not create a duplicate `CompositeValueProvider` instance in `Filter()`
- correct garbled sentence in `IBindingSourceValueProvider` doc comments
- simplify `FormValueProviderFactoryTest` (no need for Moq) and correct test name
- correct test class / file names
- `CompositeValueProviderTests` -> `CompositeValueProviderTest`
- `FormValueProviderFactoryTests` -> `FormValueProviderFactoryTest`
bda850187d