Release 2.7.6

<p>DataJoint release 2.7.6</p> <ul> <li>bug fixes</li> <li>enabled recursive populates</li> <li>added the pairing operator dj.GeneralRelvar/pair</li> <li>added dj.GeneralRelvar/show to show the header information</li> <li>changed the table definition syntax to make attribute comments optional</li> </ul