Request audio focus when playing; Pause audio when audio focus is lost; resume playing when audio focus is granted again.

This closes #88

A local file lacking the file:// or cdvfile:// prefix is not
played because resourceURL isn't validated to later on in the
play chain. avPlayer is initialized during create(), but won't
initialize without the validated resourceURL.. This closes #85

   1- [iOS] Only perform 'seek' operation if both avPlayer and avPlayerItem are ready,
        send error to client code if they aren't ready.
   2- Deplay Media File Playing by a few seconds so that 'seek' operation happens only
        after enough buffering has been done.

CB-10476 - fix problem where callbacks were not invoked on android due to messageChannel being overridden by callbackContext in every execut() call. This closes #78

This will still intermittently fail test 19 but this is more to do with
the success criteria of that rest.  rate is applied and works.

This reverts commit e7f9f048.

add support for streaming url prefixes that do not end in a file
extension
add base requirements for enabling background audio in a windows app

seekto 0 then stop playing.

stop will now behave the same when avplayer is used to play from a
stream as when avaudioplayer is used to play from a local file.

Mentioned cdvfile support in the documentation

Reworked Windows proxy to support ms-appdata file paths (temporaryFolder and localFolder)
Fixed release method to avoid Access is denied exception
Added MEDIA_RUNNING and MEDIA_ERROR states firing to record-related methods
Reworked Windows proxy to not to create Audio object in case of record mode
Adds releaseAudio to record manual test to avoid Access denied errors

github close #57
github close #58

Fix for CB-57
Updated to use avplayer when url starts with http:// or https:// for
full streaming support.

All other urls will use the standard AVAudioplayer

Fix for CB-8222
Background thread on play to prevent locking during initial load of
media.

rate is enabled, otherwise media has to be stopped and started to change rate. Fixed error getting command args