Made the API use epoch seconds for timestamps

Modified SQL queries to use UNIX_TIMESTAMP() to return epoch seconds,
modified API specs to expect numbers for timestamp arguments, added
javascript method for rending timestamps as human-readable date time
strings, and updated dummy reponder to provide integer.
Added tests for formatTimeStamp and padLeft
Merge pull request #754 from AdmiralJota/343_make_api_use_epoch_seconds

Make api use epoch seconds