Merge pull request #10 from gustafa/master

g++ added to the required packages
[sim] Clean out old simulator code and add skeleton infrastructure for new simulation mode.
[ext] Add libpion as external dependency.
[scripts] Fix bug in update code for git repos.
[engine] Port HTTP UI to new libpion (v5) API.
[engine] Add missing GetResourceNodeTree implementation.
[engine] Add appropriate comment.
Add new information regarding compatibility with old Ubuntu versions.
[engine] Fix porting bug in job submission handler.