Created dependencies model

- Added the dependencies model for projects
- The show page of a project now shows the dependencies
I'm not a huge fan of these variable names, because while they reflect the name of the section of the page where they belong, they don't reflect what they contain. It should be clear that those are arrays, so a plural name would be good, and it should be obvious that they contain project objects. I think you could use @master_projects / @sub_projects, so that naming is consistent.