Up key navigation

[birbilis]

Reader of a story should maybe only know of a linear navigation (and not case on how author nested their content).
However in StructureView they do see nested StoryPoints in non-Edit mode.

Seems currently:

UP=LEFT (PREVIOUS) and DOWN=RIGHT (NEXT) in keyboard handling,

while ESC is doing NEAREST ANCESTOR STORYPOINT in non-Edit mode and Parent StoryItem (whether it is StoryPoint or not) activation in EditMode.

HOME key goes to Home StoryItem - that doesn't have to be a StoryPoint, is supposed to be shown only once when a Story opens [and have as its next a StoryPoint] not be shown again if Story loops after next is pressed at navigation end
...[there's a chance we need to mark Ending StoryPoints [have multiple endings apart from a Single HomeStoryPoint] so that Next from them would move to the first [not Home] StoryPoint)