features now external in package simple_features
added Point2D and Dimension
restructured test files for library 'geometry'
added method truncate()
updated library 'geo', added test cases
fixed documentation details
implemented mixin for property change support
updated base layer, updated test cases
added operator * and /
added three more operators
simplefeature_layer removed from the time beeing

Going to be added again later, when the simple_features package
is integrated.
cosmetics targeted at dartdoc
renamed
cleanup, updates to recent changes in core and geometry
updated
added doc
updated test infrastructure
updated doc
updated versions of required packages