Added PQSC driver from ETH

[nielshaandbaek]

This PR adds the PQSC driver from ETH and improves it with proper error handling. It also adds the standard start and stop methods, which would be the preferred way of starting the PQSC. Secondly, the PR updates the ZI_base_instrument class to support instruments such as the PQSC that does not have an AWG.

Fixes #180.

Changes proposed in this pull request:

• Added ZI PQSC driver
• Updated ZI_base_instrument to work with instruments without an AWG.

@chellings the name of someone you want to review this pull request.

In order for the pull request to be merged, the following conditions must be met:

• travis test suite passes
• all reasonable issues raised by codacy must be resolved
• a positive review is required

Whenever possible the pull request should

• follow the PEP8 style guide
• have tests for the code
• be well documented and contain comments

Tests are not mandatory as this is generally hard to make for instruments that interact with hardware.

[chellings]

Hey @nielshaandbaek I have looked at the new commits that you have force-pushed, but it seems that they are the same commits as before, i.e., the bug with _errors_to_ignore is still there.

[nielshaandbaek]

I finally updated the HDAWG too.