track *last* hidden's class
* when a new hidden is selected, store the last hidden's class
* this prevents the new hidden selection overwriting the choice
* then use g_lastHiddenSavedClass to restore the last hidden's
  class after the new hidden's class has been stored
Merge pull request #54 from daniel-murray/topic#hiddenlastclass

Potential resolution of Issue #49

track *last* hidden's class