Grouping of Nodes for better usability

[nspielbau]

Even with the basic nodes it is already hard to find hte desired nodes. We already discussed that I would like to group the capabilities of Robots into seperate Node lists but this might be a good idea for other simmilar nodes too.
Maybe we could introduce a type value that would put it into a category such as "Adapter nodes" "Loggers" "Arithmic" "Communication"....
At the very least, the basic blocks like sequence, fallback etc. should be easily acessible, I would even say they should be buttons at the top of the editor as they are common to everything