Merge pull request #533 from vasily-kirichenko/fix-namespace-resolver

UnopenedNamespacesResolver shows the smart tag on generic type constraints and DU types
try to fix the issue with ModuleSuffix attribute
extract AssemblyContentProvider from LanguageService
AssemblyContentProvider works properly with entities included into modules with CompilationRepresentationAttribute (CompilationRepresentationFlags.ModuleSuffix) attribute
fixed: UnopenedNamespacesResolver does not work with anonymous modules properly