Updated all references to use the more technically accurate term 'ICMP Latency'
instead of 'Ping Latency' in:
- Graph titles and labels
- HTML comments
- Test assertions
- Added comprehensive tests for GraphLive.Show to ensure:
* Page renders with correct assigns
* Uses @current_organization (not @organization)
* Latency, processor, memory, and traffic graphs work
* Time range selection works correctly
* All required assigns are present
- Reordered device show page so Overall Traffic appears above Ping Latency
