v2.4.0

• chg: 222/2 accept blank
• chg: 245/2 accept blank
• chg: 760$a is not mandatory
• chg: 762$a is not mandatory
• chg: 765$a is not mandatory
• chg: 767$a is not mandatory
• chg: 770$a is not mandatory
• chg: 772$a is not mandatory
• chg: 773$a is not mandatory
• chg: 774$a is not mandatory
• chg: 775$a is not mandatory
• chg: 777$a is not mandatory
• chg: 780$a is not mandatory
• chg: 785$a is not mandatory
• chg: 786$a is not mandatory
• chg: 787$a is not mandatory / remove unused global 787 file
• chg: 950 all subfields (a-z0-9) are valid
• chg: 950 accept all indicators
• chg: 336$a is optional
• chg: 337$a is optional
• chg: 338$a is optional
• chg: 336 at least $a or $b
• chg: 337 at $a or $b
• chg: 338 at least $a or $b
• chg: 533$b optional
• chg: add 016$9 uri subfield