Relicense to GPLv2 or later

[tbm]

I'd like to distribute beancount2ledger under GPLv2 or later. Beancount is GPLV2 only.

@blais can you give permission to re-license your code (the bean-report ledger/hledger related code) under GPLv2 or later.

[blais]

Sure! Go for it, convert it to GPLv2 or later.

[tbm]

Thank you, @blais!