[IMP] ActionManager: keepSearchView option

This rev. introduces an option to doAction (keepSearchView). If set
to true, the searchView of the current action will be kept and used
by the new action (this only works if there is already an action
with a searchView, and if the new action is stacked over that one).

This is necessary for the new dashboard view.

A better solution would have been to export the state of the
existing searchView, and import it to the new one, but the current
implementation of the searchView doesn't allow to do that easily.
This will be done as soon as the searchView will be rewrote.