Improve Makefile to use cabal-sandbox for dependencies.

- Now projects required to compile are in the vendor folder
  NOTE: feel free to change name of the folder

- Flag can be used to clone development or master branch
  e.g.
  make deps       # will clone master branch
  make deps dev=1 # will clone development branch

- Add deepclean task to remove external projects and cabal-sandbox (for better test)
  Feel free to change the name of the task. Other option is cleandeps

- Make 'build' task have dependency on 'deps' task

- Add new files to .gitignore
Remove trailing whitespace line
Export TerminateChildResult record on Supervisor module. fixes #DPP-80