Added a tree function to merge small branches rather than prune them.
Added pandas-based tree summary function, and moved the constructBranchMap function into the LevelSetTree class.
Added 'LevelSetTree.firstKCluster', which finds the clusters associated with the first K splits of a tree. Renamed the old firstKCluster to LevelSetTree.firstKLevelCluster'.
Added a level set tree function to collapse leaves around a set of active nodes (LevelSetTree.collapseLeaves).
Edits to facilitate coloring level set trees more flexibly.
Moved the color 'bisque' to the end of the palette because it's hard to see in the statmaps. Also 'fixed' the error in the non-density trees in debacl.py where the floor level is 1.0 too small. Now it's 0.000001 too small. This is a quick but ugly fix - I should find the real problem and deal with it.
Final tree coloring changes.
Merge branch 'develop' of https://github.com/papayawarrior/DeBaCl into develop
Deleted extraneous 'ConstructBranchMap' function outside of the LevelSetTree class.