feature/110 Uses properties in GeppettoConfiguration.json (if present)

[jrmartin]

• Add coverage for whatever new functionality, to a JUnit test if it's backend, to a Casper Test if it's frontend
• Make sure both push and pr travis builds are passing before asking for a review

[ddelpiano]

@jrmartin overall very good and looks exactly what we need, just requested 2 tiny changes to keep the component in line with geppetto's current behaviour and to explain a little bit the getProperty function in order to be easier for other, when reading the code in a second moment, to understand what happens there.
Good job, thanks!

[jrmartin]

@ddelpiano I committed those changes (error modal button visible by default and more readable getProperty function)

[ddelpiano]

@Robbie1977 this is the pr for the error modal link that redirect to openworm, fixed now.