ControlContext :: directoryPath - Get directory path
The function opens a file dialog in order to browse a valid directory path. After selecting and confirming the directory (OK), the complete path will be returned. In order to initialize the dialog, a starting position may be passed in sFilePath. For filtering displayed entries, a file mask passed in sFileMask may be used (e.g. '*.txt').
Return value:  String value ( odaba::String  )
Implementation details
odaba::String 
ControlContext  :: directoryPath ( odaba::String &sTitle, odaba::String &sFilePath, odaba::String &sFileMask )
- sTitle - Title for window or control
- sFilePath
 - Complete file path
The complete path includes file name and directory. It might, however, be defined as absolute path starting with the root device or folder or a relative path. In order to pass no file path, an empty string ( String() ) may be passed. 
- sFileMask
 - File Mask
// following lists are equivalent: "All C++ files (*.cpp *.cc *.C *.cxx *.c++)" "*.cpp *.cc *.C *.cxx *.c++" 

