Add class ProfileProxyModel

ProfileProxyModel inherits from QAbstractProxyModel, and should provide
a layer of abstraction between the ProfileView class and the
QSqlTableModel of the "profile" table
Add empty data() overriding method

This method overrides the standard data() method of QAbstractProxyModel
Add brief to ProfileProxyModel class
Implement ProfileProxyModel::mapFromSource()

Map just row, discard column
Implement ProfileProxyModel::mapToSource() method

Map to the index in the source model with the same row and column equal
to the "id" column of the profile table
Implement ProfileProxyModel::columnCount() method
Implement ProfileProxyModel::rowCount() method
Implement ProfileProxyModel::parent() method