Fix return of icon data from site_info_service.iconFromData()
Rename site_info_servce(_test).ts -> service(_test).ts
Improve formatting of dates and month/year values in CLI output

Dates are stores as UNIX timestamps internally and month year
values as numbers with digits 'YYYYMM'.

Convert these to dates and 'MM/YY' strings respectively.
Implement tests for fetching icons from standard paths and by following page links
Implement URL fetching from add-on code
Call out to add-on code to fetch site icons