Adding support for content negotiation.
This change consists of :
1. Conneg based on request headers, supports the following 3 scenarios:
	a. ContentType property on ObjectResult set to null or is empty.
	b. ContentType property on ObjectResult set to a single content type.
	c. ContentType property on ObjectResult set to multiple content types.

2. Parsing Helpers, comparers and extensions for comparing various http headers.
3. Tests.

Open workitems:
1. Remodel JsonResult and ContentResult to be a derivation of ObjectResult.
2. Populate DeclaredType.

Conflicts:
	src/Microsoft.AspNet.Mvc.Core/Formatters/OutputFormatterDescriptor.cs
	src/Microsoft.AspNet.Mvc.Core/Microsoft.AspNet.Mvc.Core.kproj
	src/Microsoft.AspNet.Mvc.Core/OptionDescriptors/OutputFormatterDescriptorExtensions.cs
	src/Microsoft.AspNet.Mvc.Core/Properties/Resources.Designer.cs
	src/Microsoft.AspNet.Mvc.Core/Resources.resx
	src/Microsoft.AspNet.Mvc.HeaderValueAbstractions/MediaTypeHeaderValue.cs
	src/Microsoft.AspNet.Mvc.HeaderValueAbstractions/MediaTypeWithQualityHeaderValue.cs
	src/Microsoft.AspNet.Mvc/MvcOptionsSetup.cs
	src/Microsoft.AspNet.Mvc/MvcServices.cs
	test/Microsoft.AspNet.Mvc.Core.Test/Microsoft.AspNet.Mvc.Core.Test.kproj
	test/Microsoft.AspNet.Mvc.Core.Test/OptionDescriptors/OutputFormatterDescriptorExtensionTest.cs
	test/Microsoft.AspNet.Mvc.HeaderValueAbstractions.Test/MediaTypeHeaderValueParsingTests.cs
	test/Microsoft.AspNet.Mvc.Test/MvcOptionSetupTest.cs
Moving to the latest pattern of Specifying formatters using options
Responding to comments