Improve API services display on Knox Home page

Proposal:

similarly to the UI service Knox should display the logo of each API service instead of its textual representation. Clicking a log would end up opening a new modal window with the following information of that particular API service:

• service name and version
• a description of the service
• curl/pyhton examples
• JDBC query string and/or KnoxShell DataSource details

All this information should come from the service definition files (this requires to enrich the current metadata a service holds about itself in service.xml).