[db] cleans up code a bit
[db] adds notion of positive or negative altitude to bands
fixes #16
[db] adds documentation for topBand and bottomBand
[db] enforces non-0 altitudes
[db] fixes bug in Snap.bandLinks
[db] adds isPositive attribute to Band
[db] adds start of displaying bands, works on v5.xml breaks on v5_d
[db] clarifies bands topBand bottomBand
[db] Band isUsed tries to be slightly more efficient
[db] debugging why rearranging blocks does not get rid of bands
correctly
[db] seems to fix the band problem (possibly)
fixes #21 fixes #22
[db] attempts to generalize the spacer code - not quite right yet
[db] generic SpacerContainer seems to be working with Bands
[db] Removes Original BandStack and MyBand code in favor of generic
[db] changes BandStack2 to BandStack
[db] comments out a bunch of printing code
[db] replaces original BlockRibbon and MyBlock code with SpacerContainer