[db] some astetic changes and commenting
[db]
[db] changes MyBlockHorizontalSpacer into BlockItem.HorizontalSpacer
[db] changes BlockRibbon2 to BlockRibbon
[db] made the error message for forgetting to set the SpacerContainer
_spacerType easier to debug
[db] moves MyContainer to SnapContainer and MySnap to SnapItem
[db] removes unneeded debugging code from MyEmitter and MyCollector
[db] removes unused MyContainer and MySnap code
[db] removed commented out debug print statements
[db] BandItem horizontal anchors now determined by Snap extrema
fixes #20
[db] basic connections have been achieved!