started script for storage backend migrations

todo: GCS

added GCS, no GLOBALS, two methods for saving pastes and comments

use GLOBALS for verbosity again

added getAllPastes() to all storage providers

moved to bin, added --delete options, make use of $store->getAllPastes()

added --delete-* options to help

longopts without -- *sigh*

fixed arguments

drop singleton behaviour to allow multiple backends of the same type simultaneously

remove singleton from Model, collapse loop in migrate.php

comments is not indexed

tests without data singleton

fix

exit if scandir() fails

extended meta doc

CREDITS.md

@@ -31,6 +31,7 @@
 * Austin Huang - Oracle database support
 * Felix J. Ogris - S3 Storage backend
 * Mounir Idrassi & J. Mozdzen - secure YOURLS integration
+* Felix J. Ogris - script for data backend migrations, dropped singleton behaviour of data backends
 
 ## Translations
 * Hexalyse - French