#12, #7, #16 (only partially), working gwtproject.zip file

- #12  
- #7. I'm pretty sure how it works now is much better but probably still not ideal for everybody. I suggest we close #7 though, and if someone complains, we create a separate issue for the complaint (if we evaluate it makes sense to fix anything)
- The start of fixing #16. However it still does not work, because it is not clear in what direction we should go.  One option is to have our own not-very-well-working, incomplete, JS editor. Another option is to implement support for the Eclipse WTP standard JSDT tools, as users usually have these installed and would be nice to blend us into the installed mix) - just like we did for Eclipse Java JDT. 
- gwtproject.zip should be fixed to contain proper GWT project with all dependencies resovled and compilable out of the box
- The instructions in the README.md file reg. how to deal with gwtproject.zip are updated
- The SDBG group is now mentioned in the README.md file already at the beginning