allow non-rigid subassemblies
allow to set rigid property via context menu
adopt correct default colors and avoid crash due to context menu
remove unneeded display modes from viewprovider
avoid transformation of highlighted constraint
set solving precission to 1e-8
revert solving precission to 1e-6 dou to too much cases failing
Merge branch 'refs/heads/ickby-assembly' into jriegel-dev-assembly