Frontend/85 total cases

Fixes #85

[x] Modify LoadTotalCasesTask.j to get the end date as an input to that function.
[x] Add extra functions to LoadTotalCasesTask for get real and counterfactual total cases.
[x] Create a loadtotalcases() function in the infopanel component to load this data. Make sure it gets updated when the restriction dates change.
[x] Calculate relative change between natural history and Counterfacual
[x] Update placeholders the Natural history and Counterfacual panel with the new info.
[x] Create a new Utils.js file with common function between components.
[x] Deleted unused MyDatesPicker file that was still being tracked for some reason.

alan-turing-institute / CounterfactualCovid19