- 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.
- can use 'XX.empty()' instead of 'XX.size() == 0', 'XX.size() < 1' or
'XX.size() <= 0' or for simpler coding.
It also has the same number of characters as '!XX.size()' and /might/ be
more readable
- many size checking had 'XX.size() > 0', 'XX.size() != 0', or 'XX.size() >= 1'
when a simple 'XX.size()' suffices
