Qobj schema update for Pulse

[taalexander]

What is the expected enhancement?

In order to support pulse, a number of updates to the Qobj are required. There should be an ABC Qobj from which QASMQobj and PulseQobj inherit.

The pulse qobj supports a different set of Commands compared to the qasm qobj Instructions. These are detailed on [pg.36 of the openpulse specification] (https://arxiv.org/pdf/1809.03452.pdf). In addition it uses a PulseRunConfig` (#1924).

The base commands are:

• sample pulse: Refers to an entry in the pulse library (see Update RunConfig schema with pulse requirements #1924)
• frame change: fc shifts the phase of all future pulses on a channel.
• persistent value: pv holds a given value until next command on the channel.
• acquire: acquire instructs digitizers to acquire data.
• snapshot: snapshot for use with pulse simulators.

[taalexander]

Closed by #1969.