Appliance diagram

Add a new view in the web-ui to display appliance
as a diagram. The diagram should contains details
of disks, cpus, network cords, memory grids
Merge branch 'master' of https://github.com/rockstor/rockstor-core
rollback appliance view changes
Metric Collection switch on dashboard

Added Metric Collection switch on top end of left navigation on dashboard
which controls starting and stopping of Data Collector service.
Merge branch 'issue#450_data_collector_service_switch_on_dashboard' of https://github.com/kamal-gade/rockstor-core into kamal-gade-issue#450_data_collector_service_switch_on_dashboard
Cleanup polling for data-collector

Add a cleanup method for the DashboardConfig view
Call dashboardconfig view cleanup from home view cleanup
Add startPolling to dashboardconfig render
Merge pull request #473 from kamal-gade/issue#450_data_collector_service_switch_on_dashboard

Issue#450 data collector service switch on dashboard
Use template for error messages.
Merge pull request #480 from Mchakravartula/issue#321_use_template_for_err_msg

Use template for error messages.