Add trackDimension.
Add trackDimension.

Now there is a track selector to show just the packages within a single
track. There is currently no ordering between tracks which is most
likely not an issue as there is little information in the relationship
of tracks that would not be better gleaned from git.

baldwinn860/gapid,google/agi,dsrbecky/gapid,google/gapid,pmuetschard/gapid,pmuetschard/gapid,baldwinn860/gapid,google/gapid,Qining/gapid,pmuetschard/gapid,google/agi,dsrbecky/gapid,baldwinn860/gapid,baldwinn860/gapid,Qining/gapid,dsrbecky/gapid,Qining/gapid,google/agi,dsrbecky/gapid,google/agi,baldwinn860/gapid,google/gapid,baldwinn860/gapid,Qining/gapid,baldwinn860/gapid,Qining/gapid,google/gapid,pmuetschard/gapid,google/gapid,Qining/gapid,pmuetschard/gapid,dsrbecky/gapid,pmuetschard/gapid,google/gapid,dsrbecky/gapid,pmuetschard/gapid,google/agi,Qining/gapid,pmuetschard/gapid,google/agi,dsrbecky/gapid,Qining/gapid,baldwinn860/gapid,google/gapid,google/agi,google/agi,google/gapid,dsrbecky/gapid