objectRegistry fixes

- objectRegistry gets a rename() that also adjusts the dbDir
- cloud reworked to use static variables subInstance and defaultName.
  This avoids writing "lagrangian" everywhere

string fixes
- avoid masking of std::string::replace in string.H
- avoid old strstream in PV3FoamReader

applications/utilities/parallelProcessing/decomposePar/lagrangianFieldDecomposerDecomposeFields.C

@@ -88,7 +88,7 @@ tmp<IOField<Type> > lagrangianFieldDecomposer::decomposeField
             (
                 field.name(),
                 procMesh_.time().timeName(),
-                "lagrangian"/cloudName,
+                cloud::subInstance/cloudName,
                 procMesh_,
                 IOobject::NO_READ,
                 IOobject::NO_WRITE