* Default BTab uses view's name property as tab label, so
SetLabel changes that value. However, view names are important
for yab and this would cause inconsistencies in view lists yab
stores for referencing them by name. Views attached to tabs would
not be removed because there is no name "Tab1" in the index
(there is "Test1", which is the view's original name).
Later, when asking for view with the same name created later yab
could get wrong view (if lucky) or crash (if unlucky).
This commit fixes that by storing original name in YabView
property, and using that for removing views from the hierarchy.
* Fixes#5.
