De-Select feature in feature tree

This PR adds the possibility to de-select a feature in the feature tree. The interaction with the elements in the feature tree now better resemble the interactions in other elements as catalog tree, tools menue etc. mentioned in #980.

It's alsow re-factoring the inter-directie handling of tooltip and feature tree (now using callback function instead of working directly on specific options).

In addition, the tooltip is now closed when the feature tree window is closed.

Note that the handling of the events resulted in more complicated code than I actually desired. The culprit for this is the requirement to be able to select elements in multiple ways (by click, by keyboard, by tab) inside the window.

This has been tested in FF26, chrome32 and IE11. If someone could test it in Safari/iOS?