[BUGFIX] Correction of Filelink of FAL in linkvalidator

Add a fetchType function for linkvalidator to take
FileLinktype class for "file:XXX" media instead of internalLink class.

Make a first validation with "retrieveFileOrFolderObject" to
check if file exist in a database.

Make a second validation on the file "physically" on the server.

Resolves: #66895
Releases: master, 6.2
Change-Id: Ife0ab588e0ac4eb932cca3d6545f243bbcddc7ae
Reviewed-on: http://review.typo3.org/39464


Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Frans Saris <franssaris@gmail.com>