new translations labels for mail and rest, and we now pass the 2F prefix
to templates. It's not used in the default skin, but it should help in
cases where extra second factors are used to offer the user a more
helpful prompt message
This commit adds a manager interface to declare multiple instances of a
single 2F module, in a manner similar to Combination.
An additional portal code reads the `sfExtra` variable to load the
declared modules.
An empty rules means the module will be always active.
