Fix for #1192 - Support customizing reflected model through attributes

This adds support for attributes which interact with reflected model.
These conventions are applied after all of our built-in constructs so that
you can see and modify the results.
Removing declaration expressions
Adding support for ViewLocationExpanders to allow modifying view locations
without changing the view engine.

Fixes #1039
Reacting to Razor changes
Removing Overloading and Automatic verb-mapping

This change removes WebAPI-style method parameter overloading and the
automatic mapping of 'unnamed' actions based on method names. For all
practicaly purposes, this change restores the MVC5 behavior for action
selection.

WebAPI-style overloading will be brought back in the future via a set of
opt-in constructs.
Cleanup namespaces and Task.FromResult
Modifying test project.json to allow building on Mono
[Fixes #429] FileResult

1) Implemented FilePathResult to efficiently return files from disk.
2) Implemented FileStreamResult to return content from a stream.
3) Implemented FileContentResult to return content from a byte array.
Changes to support PageExecutionContext in Razor
Fixes #1083
Changes to make EnableInstrumentation conditionally enabled
Calculate `ModelMetadata.DataTypeName` based on metadata
- helps MVC helpers like `@Html.EditorFor()` select the correct template
- #933

nit: add XML doc for `DataTypeName` in base `ModelMetadata`
Correct minor problem in `CachedDataAnnotationsModelMetadata.ComputeDisplayFormatString()`
- only affects an extreme corner case: user sets `metadata.EditFormatString` then reads
  `metadata.DisplayFormatString`
- an extreme case because `EditFormatString` is normally set only when
  `DisplayFormatString` is set and, if set, it's to the same value
- happened to see this while updating `CachedDataAnnotationsModelMetadata` for this PR

nit: an -> a in an adjacent XML comment in `CachedDataAnnotationsModelMetadata`