Fixes search entry losing typing focus

When the search entry was out of focus and types were redirected to it,
if the current selected application was hidden by the filtering, both
the holder and entry lost focus. This stopped the typing event
redirection. Now the entry is always focused when typing.
Clear search entry when switching from Apps to Favorites

Took two clicks because of a loop in the logic (setting to empty
also invokes setting the tab).

Fixes #44
Merge pull request #61 from hordepfo/search-entry

Search entry