Amex support

[csingley]

There are two issues that need to be addressed to restore Amex connectivity:

1. As referenced in this issue, Amex has something weird going on with its HTTP Accept header. Apparently they require that this header include application/xml with SOME quality weight - ANY quality weight. Writing Accept: application/xml;q=1 is sufficient, whereas Accept: application/xml fails. Adding anything else with whatever quality doesn't faze Amex; it just needs to see that MIME type somewhere with some quality. A fix for this was committed in a59f1b2

2. Now that Amex is deigning to speak OFX with you (rather than just dropping you with HTTP errors), you can log in... but it will complain that it can't find the account you're asking for. The STATUS subaggregate within CCSTMTTRNRS contains SEVERITY: ERROR, CODE: 2003 i.e. Account not found. If you send an ACCTINFORQ, it turns out that every ACCTID has all but the last 4 digits of the card# obfuscated. If you use these obfuscated card# verbatim for the ACCTID in your CCSTMTRQ (you can put them into your ofxget.cfg), then the statement request succeeds.