Added functionality to use asynchronous versions of the setter functions to speed up device configuration

[nielshaandbaek]

The purpose of this PR is to add support for setting device settings faster by not waiting for a response from the server. The functionality is implemented using asyncBegin and asyncEnd added to the base class of the ZI drivers. Use the functionality like this:

uhf = UHFQC(...)
uhf.asyncBegin()
uhf.sigouts_0_on(1)
uhf.sigouts_1_on(1)
uhf.sigouts_0_imp50(True)
uhf.sigouts_1_imp50(True)
uhf.asyncEnd()

The driver will wait for all the writes to complete after asyncEnd() is called.

Fixes #192.

Changes proposed in this pull request:

• Added asyncBegin and asyncEnd methods to ZI_base_instrument
• Updated such that asyncSetInt and asyncSetDouble are used after asyncBegin
• Updated such that asyncEnd calls the daq.sync() function causing the driver to wait for all writes to complete.
• Added unit test of new functionality.
• Updated MockDAQServer to support asynchronous versions of the set methods.

@mention 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:

• test suite (Github actions) 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.

[nielshaandbaek]

Unfortunately, our API does not currently have asynchronous versions of the functions that setc and setv map to, namely setComplex and setVector. Therefore, I couldn't implement the functionality for those functions.