Detect preloaded about:superstart page as blank
(extensions.superstart.page.preload = true)
(part 2 for #142)
Use configurable object to store empty tab labels
(preparation for #143)
Rename: windowsObserver -> privateTab
(better for debug things like built-in profiler)
Add window.privateTab.tabLabelIsEmpty() API
(#143)
Add documentation for window.privateTab.tabLabelIsEmpty() API
(#143)