Update Schwab CSV to support latest format

[1997cui]

1. schwab_csv importer raises AssertionError because CSV has no title line #218 I had a similar issue, so instead of reading the account number from the first line, we read it from the file name, so DO NOT change the default Download filename
2. Schwab brokerage transcations csv changes and unhandled BrokerageActions #171 This partially resolved this by changing the line format.
3. I added more transaction types to the best of my knowledge.

This change needs to adjust the ledger account name. I've updated the tests, please see journal.beancount file for the changes needed.

I only have a brokerage account, so I cannot test the Intelligent Profilio and Checking account, but I updated them to the best of my knowledge. At least, this PR gets the brokerage account only working again.

[carljm]

I no longer use the Schwab CSV importer (I found it too painful because Schwab changes their format too frequently), so I can't personally test this. But if you get it passing CI I'll be willing to merge it on the basis that it works for you.

[sammyvancleve]

A little late to the party, but just tested this fix and it looks like Schwab has further changed their formatting. Specifically, formatting the date in the transactions header from MM/DD/YYYY to YYYY/MM/DD -- manually changing the header of the transactions CSV took no time and worked for me.

As for the positions CSV, this worked for me if I exported the CSV from 'Legacy View', but their new default CSV was incompatible. I might try to update this fix but considering how often they seem to change their formatting I don't know how useful it would be long-term.

[carljm]

FWIW I think the Schwab csv importer should perhaps be abandoned/removed. I contributed it originally but I've found they change their CSV formats constantly and so I've stopped using it, maintaining it seems like more work than manually entering transactions. (Though I guess that depends how many transactions you have.)