Browsing French translation

1698.

The version number is defined in a class attribute named <code>persistenceVersion</code>. This is an integer which will be stored in the .tap file along with the rest of the instance state. When the object is unserialized, the saved persistenceVersion is compared against the current class's value, and if they differ, special upgrade methods are called. These methods are named <code>upgradeToVersionNN</code>, and there must be one for each intermediate version. These methods are expected to manipulate the instance's state from the previous version's format into that of the new version.