monitoring : add statistics pages system

monitoring/cockpit/castormon/cockpit/views.py

monitoring/cockpit/castormon/staticfiles/css/base.css

monitoring/cockpit/castormon/staticfiles/js/scripts.js

...ng/cockpit/castormon/staticfiles/js/statistics-scripts.js

monitoring/cockpit/castormon/templates/cockpit/base.html

monitoring/cockpit/castormon/templates/cockpit/sls.html

...castormon/templates/cockpit/statistics/c2alice_rates.html

...castormon/templates/cockpit/statistics/c2atlas_rates.html

...t/castormon/templates/cockpit/statistics/c2cms_rates.html

.../castormon/templates/cockpit/statistics/c2lhcb_rates.html

...astormon/templates/cockpit/statistics/c2public_rates.html

monitoring/cockpit/castormon/urls.py