Implemented new class FocusManager that manages focus in MoreMenu

Implemented new class FocusManager that manages focus in MoreMenu

[Issue]    https://bugs.tizen.org/jira/browse/TT-183
[Problem]  There was a problem with navigation in MoreMenu.
[Cause]    Disabled "Add to bookmarks" button was blocking moving
           the focus.
[Solution] This is a workaround (because 'custom focus chain' API
           did not work properly. I have created new class that
           stores objects to focus and implements mechanism of
           mooving the focus.
[Verify]   Launch browser > Navigate to More menu > Use arrows to
           move the focus.

Change-Id: I3942e97c3176a204fc2ccd8738344f179cf1e89b