Port Queue Grouping

It is possible for the WMS to specify that bins in the port queue belong together in groups. Bins within one
such group can have their sequence changed by AutoStore to optimize performance. It is still important that
the WMS plans and optimizes the Port Queue sequence, because AutoStore will plan the delivery according
to the given sequence. But when an openbin command is received, AutoStore will evaluate if another bin can
be delivered faster than the first one. The openbin response includes the selected bin.

Port queue groups cannot be nested inside each other.

The begingroupportqueue method will implicitly end the current group, and start a new group. The bins
appended to the port queue after begingroupportqueue will belong to the same group, until the group is ended
with endgroupportqueue or begingroupportqueue. Bins are not required to belong to a group. Bins appended
after endgroupportqueue do not belong to a group, and will be delivered strictly in the specified sequence.

Example response from getportqueue (with comments):

<?xml version="1.0" encoding="utf-8"?> 
<response> 
  <params>
    <bins> 
			<bin_id>11</bin_id> -- outside group, will be delivered first 
			<begingroup></begingroup> 
				<bin_id>101</bin_id> -- 101, 102, 103 are in the same group 
				<bin_id>102</bin_id>
				<bin_id>103</bin_id> 
			<begingroup></begingroup> 
				<bin_id>201</bin_id> -- 201, 202, 203 are in the same group 
				<bin_id>202</bin_id>
				<bin_id>203</bin_id>
			<endgroup></endgroup> 
			<bin_id>12</bin_id> -- outside group (specified sequence)
			<bin_id>13</bin_id> -- outside group (specified sequence)
			<begingroup></begingroup>
				<bin_id>401</bin_id> -- 401, 402, 403 are in the same group 
				<bin_id>402</bin_id> -- group is not yet terminated,
				<bin_id>403</bin_id> -- appendportqueue into same group
	</bins>
 </params>
</response>

Please note that AutoStore removes superfluous begingroup/endgroup elements.