ENH: improve flexibility of error, messageStream output

- provide a plain stream() method on messageStream to reduce reliance
  on casting operators and slightly opaque operator()() calls etc

- support alternative stream for messageStream serial output.
  This can be used to support local redirection of output.
  For example,

     refPtr<OFstream> logging;   // or autoPtr, unique_ptr etc

     // Later...
     Info.stream(logging.get())
        << "Detailed output ..." << endl;

  This will use the stdout semantics in the normal case, or allow
  redirection to an output file if a target output stream is defined,
  but still effectively use /dev/null on non-master processes.

  This is mostly the same as this ternary

      (logging ? *logging : Info())

  except that the ternary could be incorrect on sub-processes,
  requires more typing etc.

ENH: use case-relative names of dictionary, IOstream for FatalIOError

- normally yields more easily understandable information

applications/test/foamVersion/Test-foamVersion.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -52,7 +52,7 @@ void testExtraction(const std::string& str)
 int main()
 {
     Info<< "\nVersion information (function)" << nl;
-    foamVersion::printBuildInfo(Info().stdStream());
+    foamVersion::printBuildInfo(Info.stdStream());
 
     Info
         << "\nVersion information (macros)" << nl