Bluetooth: add "Accept all files" option for incoming files via Bluetooth [3/3]

  This patch will let the OBEX server read "Accept all files" option
before it starts to check mime-type whitelist.
  If not enabled,the check process will go on as usual.
  If enabled,mime-type checking will be skipped.

  Use together with https://gerrit.omnirom.org/6782/
and https://gerrit.omnirom.org/6783/

Change-Id: I4a485358807cba2eb7c06477b5f28d402f7cdc6b