Consider removal of destroySegment

[breznak]

Off Topic: I think that the HTM would work just as well if we never allowed for destroying segments (untested). Instead of destroying segments just remove all of the synapses. The use-case for destroying segments is when the TM is full and you want to add a new thing to it. In this situation, the destroyed segment will immediately recreated with different synapses. This would allow us to get rid of the segmentOrdinals and segment.id ~ @ctrl-z-9000-times

A thing to try, would be nice simplification of the code.

From #537 , related #161