- using 'nil' type to write geometry only, in the future we could fallback to 'null'
writer and hook in arbitrary formats from surfMesh
- IOobject gets writeEndDivider() static method
- removed the previously added fileName type(), isDir(), isFile() methods.
- added optional bool parameter to isFile() function to explicitly
enable/disable the check for gzip files.
- fixed minor bugginess where the default usage of isFile() would result in
false positive matches.
- be slightly more stringent and use isDir() and isFile() instead of
exists() function when we actually know the expected type.
