Add transcode from beancount/ledger/hledger to knut

[PaulsTek]

Right now I can create a beancount ledger from a knut ledger file, but not the opposite - the syntax is sufficiently different that I cannot just use find and replace. So far these are the issues I have, and there may be others, and need to make my own transcoder:

• replace ";" with "#" for comment lines
• remove "*" after date
• remove leading spaces from debit account row
• combine debit and credit account rows
• other differences??

eg: beancount syntax: 2020-01-10 * "CITY UTILITY PAYMENT" Assets:WellsFargo:Chk -10.00 USD Expenses:Home:WaterAndTrash 10.00 USD

knut syntax: 2023-01-05 "CITY OF DENTON UTILITY" Assets:WellsFargo:Chk Expenses:Home:WaterAndTrash -70.00 USD

[sboehler]

Great idea! The complexity is mostly on the side of parsing the formats of the other tools, I don't think I would like to maintain a parser for all these formats in knut's code base. Having a standalone converter would make a lot of sense though - if you publish yours, happy to link it in the docs.