Add a member var to hold the app's settings

- This is a variable of type QMap<Qstring, QVariant>, that should be
  added to controller.h

- Add a new private method "initializeSettings()" to controller.h

- createCa() should be called before initializeSettings, reflect this
  fact in the declaration of methods in controller.h
Implement Controller::initializeSettings()

- The method inserts the relevant key,value pairs into the qmap, once
  inserted, the method updates the settings.

- Add this method to the list of methods being called in the
  constructor.

- Add mSettings to the list of arguments in the call to the constructor
  of the LocalSettingsDialog class.
Update constructor of LocalSettingsDialog class

- Add a parameter of type QMap<QString, QVariant> to the constructor of
  the LocalSettingsDialog class.
Implement new constructor of LocalSettingsDialog

- The new constructor should populate the form using the pairs of the
  QMap received.

- The QMap received in the constructor should be stored in a member var.

- The LocalSettingsDialog::accept() method updates the settings object
  using the corresponding properties of the widgets.
Reset values of LocalSettingsDialog's widgets

- 1 for all widgets dealing with the radius of some neighborhood

- 0 for all other widgets
Load settings from a master settings file

- This file is named "settings.xml".
- If not found upon starting the application, then it must be created.
Remove mSettings from controller and local dialog

- localSettingsDialog should populate itself from the master settings
  file.
Update settings.xml from settings dialog
Add import & export capabilities

- This feature is incomplete.
Add showEvent to LocalSettingsDialog

- During this event, the form is populated according to the information
  containded in the settings.xml file.
Fix a bug in exportSettings() and importSettings()

- The bug was caused by not checking first whether the file name
  returned by the dialogs was empty or not.
Fix a bug in Controller::exportSettings()

- The settings file must be copied to the chosen destination, only if no
  file with the same name already exists.
Fix a bug in controller.cpp

- When starting the program, the cellular automaton must be reinitialized
  after the settings file has been loaded.