idgames_db_dump: fix URLs to make JSON API requests
XMLParser: issue 74: ignore 'textfile' when parsing latestfiles
JSONParser: close #26; parse meta, latestfiles, get requests

- Since the JSON parser should parse the same requests as the XML
  parser, this change should also resolve issue #46, issue #48,
  issue #62, issue #64, issue #74
project: close #80: keep track of unsuccessful requests/parses
JSONParser: correctly copy out data from 'get' request
idgames_db_dump: clarify error message after calling parser