ENH: allow "<case>", "<system>" ... in the string expansions (issue #792)

- the expansions were previously required as slash to follow, but
  now either are possible.

    "<case>", "<case>/" both yield the same as "$FOAM_CASE" and
    will not have a trailing slash in the result. The expansion of
    "$FOAM_CASE/" will however have a trailing slash.

- adjust additional files using these expansions

src/OpenFOAM/interpolations/interpolationTable/interpolationTable.H

@@ -42,7 +42,7 @@ Description
     Read csv format:
     \verbatim
         readerType      csv;
-        file            "$FOAM_CASE/constant/p0vsTime.csv";
+        file            "<constant>/p0vsTime.csv";
         hasHeaderLine   true;   // skip first line
         timeColumn      0;      // time is in column 0
         valueColumns    (1);    // value starts in column 1