fix bug #80, new option to filter by gender or dead/alive

The idea behind the filter options (see #18) is that in the final version of this function a user should be able to set the filter options shown in the filter bar on top of the gray message, but this is not working up to now. So this is more a beta version of this function. The administrator can use the filter options (using the control panel), but not the users of the tree. If you as an admin are the only user of your tree, you can use this function, if there are other users, then you should disable the filter option for your tree at the moment. To inform the users that the results are filtered, there is the gray message bar shown at the moment.