Fixes for Web Connector, and support for uc_qb.

QBWC didn't seem to think that connectionError() was implemented correctly, and getLastError() didn't appear to be useful as written. The first part of this patch addresses these two issues.

The second half adds the retCount to the $response if one was returned from QuickBooks, because a lot of the response callbacks in uc_qb needed them. I didn't see any other way to get to that data, so receiveResponseXML() ought to pass it along.

The other changes are stylistic, and based mostly on my own preferences.