Cleanup and fix cookies handling

 * The cookie jar iterator now use a BObjectList instead of a BList
 * Add a convenience method to the cookie jar to add a cookie by BUrl
and raw cookie string.
 * Remove some methods in BNetworkCookie that could lead to invalid
cookies (cross-domain or with no domain at all).
 * Make the cookie parsing able to report errors
 * Fix off-by-one error in domain cookies validation.
Don't send a chunked transfer terminator for non-chunked transfers.

 * Fixes oversight from previous change.
 * Thanks hamishm for watching !