Merge remote-tracking branch 'lukaszmluki/master'

* lukaszmluki/master:
  ftp: enhanced error handling
  ftp: reconnect on seek
  ftp: move common commands code to function
  ftp: enhanced status code handling
  ftp: reconnect on read
  ftp: move create control connection to function
  ftp: credentials moved into FTPContext
  ftp: rename function name
  ftp: formatting and typos fixes

Merged-by: Michael Niedermayer <michaelni@gmx.at>