* removed neighbour selectors (not really needed at all). Improves compilation speed, memory usage and binary size!
* removed clustering specific code in favour of more generic property code
* added GetEdgeHistogram()
* renamed some functions/options ("degree"->"vertex")


git-svn-id: https://svn.forked.de/graph-tool/trunk@9 d4600afd-f417-0410-95de-beed9576f240