Build on Ubuntu 15.10
I've made some changes to the code base to enable builds on Ubuntu 15.10. The changes relates to calls to Boost > 1.56, so the changes should help for preparing RobWork for Ubuntu 16.04.
I've also added static_cast<> to some comparisons throughout the code to get rid of warnings. Code in etx/ is untouched.
Svn patch is attached.