Merge pull request #44 from hjanetzek/master

roof:shape=round added
Merge pull request #47 from hjanetzek/master
test whether ridges/edges are connected
- use roof:height from building:part as default for complex roof
- test if ridge/edge lie on the boundary, pnpoly is not reliable in this case
  - this way single sloped roof can be defined by adding only one ridge on the outline