Create directory. If the directory specified at the parameter exists, it is removed and created.
MCMD::mkDir(dirName[,rmExistingDir])
dirName - Directory name to create.
rmExistingDir - When true is specified, if dirName exists, it is removed and created.
# Create the directory ./folder.
# Do not do anything if the directory exists.
> MCMD::mkDir("./folder")
# When true is specified at the second, if ./folder already exists, delete the existing
directory and create a directory .
> MCMD::mkDir("./folder",true)