[Hydro] Issue/heavy payload rebased

This PR supersedes #78 
It is rebased to latest hydro-devel, it adresses the comments from @gavanderhoorn and has some beautifying changes guaranteeing conformity
The value for ```max_payload``` derives from what the panel allows to be set for payload.
I.e. - for the UR10 - if you enter a value higher than 20, the panel complains. (For UR5, the value is 10 respectively)