Refactored server preferences.
Previously, the hostName was stored in the preferences. Now the code (ex : US) is stored and the hostName is matched in the PADServer enum.
This allows to update the hostname easily (no need to force the user to re-check the updated server or to write custom code to update the preferences)
Fixed #52 : updated NA hostname introduced in 7.2.1
Bumped version to 1.4.9