Add ascanct parameter output

[johanfforsberg]

Adds a table with some helpful output of the motor settings that are about to be used in a continuous scan.

In order to implement this, we had to change how the header of the scan table is output; it is now printed when the first point arrives, and not immediately. This also prevents some issues with info/debug messages appearing after the header.

The original issue #692 also suggests showing the restored settings after the scan but for similar reasons (see issue #1651) it is currently commented out. It can be added in whenever that issue is solved.

Example:

Door_2_1 [5]: ascanct mot10  0 10 10 0.1 0.1
ScanDir is not defined. This operation will not be stored persistently. Use "expconf" or "newfile" to configure data storage (or eventually "senv ScanDir <abs directory>")
Scan #31 started at Thu Jul  8 13:05:35 2021. It will take at least 0:00:00
Motor positions and relative timestamp (dt) columns contains theoretical values
 Motor    Velocity   Acceleration   Deceleration  Start   End  
 mot10       5            2              2          -5     16  

 #Pt No    mot10      ct09      ct10      ct11      ct12       dt   
   0         0        0.1       0.2       0.3       0.4        2    
...

Opinions on how the output should be formatted are very welcome.

Fixes #692

[teresanunez]

Thanks for the implementation. I thinks it is nice like this. The only comment that I could do: perhaps
should be put something about what the number of the header are ?. I mean to specify that they are
parameters computed and used for internal use in the continuous scan. I don´t know, it is only a
question/doubt. I am not sure if every user would not what is that.

[yimli]

Thanks for you comment. It is somehow not very clear that what the number of the table means. So should we add a explanation sentence before the information table? Maybe that will make the output look heavy?

[johanfforsberg]

We have updated the output a bit:

 Motor   Velocity[u/s]   Acceleration[s]   Deceleration[s]    Start[u]   End[u] 
 mot10         10               2                 2             -10        22   
 mot11         0                0                 0              2         2    

Also note that this table will be output for each waypoint, e.g. when doing a mesh scan, interleaved with the scan output. This is necessary since the motor settings will be changed.

[reszelaz]

I think this PR makes the following tests fail:

=========================== short test summary info ============================
FAILED ../../../usr/local/lib/python3.5/dist-packages/sardana-3.1.2a0-py3.5.egg/sardana/macroserver/macros/test/test_scanct.py::AscanctTest::test_ascanct_macro_runs
FAILED ../../../usr/local/lib/python3.5/dist-packages/sardana-3.1.2a0-py3.5.egg/sardana/macroserver/macros/test/test_scanct.py::AscanctTest::test_ascanct_macro_runs_2
FAILED ../../../usr/local/lib/python3.5/dist-packages/sardana-3.1.2a0-py3.5.egg/sardana/macroserver/macros/test/test_scanct.py::AscanctTest::test_ascanct_macro_runs_3
FAILED ../../../usr/local/lib/python3.5/dist-packages/sardana-3.1.2a0-py3.5.egg/sardana/macroserver/macros/test/test_scanct.py::AscanctTest::test_ascanct_macro_runs_4
FAILED ../../../usr/local/lib/python3.5/dist-packages/sardana-3.1.2a0-py3.5.egg/sardana/macroserver/macros/test/test_scanct.py::A2scanctTest::test_a2scanct_macro_runs
FAILED ../../../usr/local/lib/python3.5/dist-packages/sardana-3.1.2a0-py3.5.egg/sardana/macroserver/macros/test/test_scanct.py::MeshctTest::test_meshct_macro_runs

I think the tests need to be adapted to the new output lines.

[reszelaz]

I will work on the tests to fix the CI.

[reszelaz]

Those tests are already fixed with 99a18fd.