* Remove IAssemblyProvider.
* Remove DefaultAssemblyProvider in favor of DefaultAssemblyPartDiscoveryProvider.
* Update AddMvcDnx to add the list of DNX discovered assemblies to the list of application parts.
- aspnet/Coherence-Signed#187
- remove `<RootNamespace>` settings but maintain other unique aspects e.g. `<DnxInvisibleContent ... />`
- in a few cases, standardize on VS version `14.0` and not something more specific