typeIOobject: Template typed form of IOobject for type-checked object file and header reading

used to check the existence of and open an object file, read and check the
header without constructing the object.

'typeIOobject' operates in an equivalent and consistent manner to 'regIOobject'
but the type information is provided by the template argument rather than via
virtual functions for which the derived object would need to be constructed,
which is the case for 'regIOobject'.

'typeIOobject' replaces the previous separate functions 'typeHeaderOk' and
'typeFilePath' with a single consistent interface.

applications/utilities/preProcessing/setFields/setFields.C

@@ -58,7 +58,7 @@ bool setCellFieldType
     word fieldName(fieldValueStream);
 
     // Check the current time directory
-    IOobject fieldHeader
+    typeIOobject<fieldType> fieldHeader
     (
         fieldName,
         mesh.time().timeName(),
@@ -67,9 +67,9 @@ bool setCellFieldType
     );
 
     // Check the "constant" directory
-    if (!fieldHeader.typeHeaderOk<fieldType>(true))
+    if (!fieldHeader.headerOk())
     {
-        fieldHeader = IOobject
+        fieldHeader = typeIOobject<fieldType>
         (
             fieldName,
             mesh.time().constant(),
@@ -79,7 +79,7 @@ bool setCellFieldType
     }
 
     // Check field exists
-    if (fieldHeader.typeHeaderOk<fieldType>(true))
+    if (fieldHeader.headerOk())
     {
         Info<< "    Setting internal values of "
             << fieldHeader.headerClassName()
@@ -204,7 +204,7 @@ bool setFaceFieldType
     word fieldName(fieldValueStream);
 
     // Check the current time directory
-    IOobject fieldHeader
+    typeIOobject<fieldType> fieldHeader
     (
         fieldName,
         mesh.time().timeName(),
@@ -213,9 +213,9 @@ bool setFaceFieldType
     );
 
     // Check the "constant" directory
-    if (!fieldHeader.typeHeaderOk<fieldType>(true))
+    if (!fieldHeader.headerOk())
     {
-        fieldHeader = IOobject
+        fieldHeader = typeIOobject<fieldType>
         (
             fieldName,
             mesh.time().constant(),
@@ -225,7 +225,7 @@ bool setFaceFieldType
     }
 
     // Check field exists
-    if (fieldHeader.typeHeaderOk<fieldType>(true))
+    if (fieldHeader.headerOk())
     {
         Info<< "    Setting patchField values of "
             << fieldHeader.headerClassName()