Fixed copyright year for some files
Bug fix: Application crashes when loading from an empty playlist

Added check for Playlist::isEmpty() when updating the file position in
the status bar.
Refactored Filter class

Minor changes to implementation and comments. No changes to interface.
Bug fix: Opening an archive file always moves to the last viewed file

When opening an archive, the playlist should only move to the last
viewed file if the archive was opened from the previous session. If a
user opens an archive through the File Open dialog, the playlist should
always be initialized to the first file in the archive.
Changed Utility class to namespace

Minor changes to comments and coding style.
Refactored ImageSource and Playlist to store ImageInfo objects as indexed pairs

Each entry in the ImageSource list is now a pair containing an integer
and ImageInfo pointer. The integer is used to replace the ImageInfo::_id
property and keep track of the index of the image in the list, even when
the list is shuffled.
Bug fix: Playtlist is not shuffled when filtering out the current image

Added temporary variable to the Playlist class to keep track of the
order type while the playlist is shuffled.
Bug fix: Playlist reloads current image when filtering, even if the current image doesn't change

Added check to ensure the Playlist class only emits an indexChanged
signal when the index changes.
Code style changes to ImageInfo class

Removed "this->" from private variable calls and modified comments.
Bug fix: Filtering an empty list causes a crash

Added a check to ensure the playlist isn't empty when reloading from the
image source and added a missing indexChanged() signal call when calling
find().

Additionally, did minor refactoring.
Bug fix: Application crashes when no playlist is loaded

Added empty constructor to Playlist class and initialized the MainWindow
with an empty playlist.
Refactored QSettings usage in MainWindow class

Removed unecessary values and added grouping. Moved the ini location to
the user's application settings directory.