Modify add profile dialog

Introduce a QPushButton in place of the existing QToolButton, the
picture preview will be displayed in a QLabel.
Rearrange layout of part of the dialog.
Add supported image files for profile picture

Add support for .gif and .bmp
Load picture preview

Picture of a profile is now loaded as a preview into the label
Modify pixmap retrieval

Store temporary the original profile picture in a private QPixmap, use
the private variable to initialize the Profile object
Insert profile into the db

New function in VRDatabase performs the insertion of the profile in the
database of the application