Front end counterfactual calculation functionality

[crangelsmith]

Fixes #76

• Refactoring InfoPanel with all important dates as state variables and now datepickers declared in this component
• Delete MydatePicker component
• Refactoring Histogram to inherit the important dates
• Refactoring LoadDailyCasesTask.js to use date range information and restriction dates to fetch data from real and counterfactual cases
• Addressing comments from PR #73

I this PR I focused on the functional side: make the counterfactual recalculation work. There is a bunch of aesthetical improvements that should be made in a next PR.

[crangelsmith]

Example of the counterfactual recalculation in the front end: