[Cashtab] Change date format

Summary: Changed date strings to match request in task T2058. Each instance of toLocaleDate() has been updated to include an options parameter which presents the date in the MMM-dd-yyyy format.

Test Plan:
cd web / cashtab && npm start
In the wallet tab
Ensure Tx dates are formatted correctly.
Navigate to the eTokens tab
Select an eToken
Ensure genesis date is formatted correctly.
In browser settings, change locale and run through test plan again.

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Subscribers: emack

Differential Revision: https://reviews.bitcoinabc.org/D10652