Deprecate outputSEQXfile method (use forge instead)

[astafan8]

While working with AWG5208 and using the example notebook from broadbean as the reference, using outputForSEQXFile method of the Sequence object together with makeSEQXFile method of the AWG driver like below resulted in an error 1331 on the AWG device upon loading the successfully created and transmitted SEQX file:

...
seqx_args = sequence.outputForSEQXFile()
seqx_file = awg.makeSEQXFile(**seqx_args)
...

As @WilliamHPNielsen suggested, forging the sequence should be used instead (and it indeed worked):

...
forged_sequnce = sequence.forge()
seqx_file = awg.make_SEQX_from_forged_sequence(forged_sequence)
...

ToDo:

• deprecate outputForSEQXFile method of the Sequence object with the message of using forge instead
• update the example notebook to use forge

@WilliamHPNielsen @sohailc