Add default logging for bad IPC messages

[jonathonmcmurray]

kdb+'s default behaviour when a malformed IPC message is received is to signal 'badmsg and close the offending connection. This is somewhat unhelpful for investigating e.g. when you have multiple feedhandlers etc. - there's no way of knowing which one sent the bad message.

kdb+ has a handler, .z.bm, that will be called (if defined) when a malformed IPC message is received. Currently TorQ doesn't define this handler.

I think we should put in a default handler - we can use the handle the bad message was sent over to look up in .clients.clients and/or .servers.SERVERS and get some more identifying information e.g. host, username etc. (obviously if multiple feedhandlers run on same host, this will only really be useful if each uses a unique username). Then we can print a more descriptive error log to identify the offending message sender & allow for further investigation.

We can probably also store the offending raw message, similar to the example on code.kx.com.