941 append scaling to ws name

[GuiMacielPereira]

Summary

• Created new class that returns name of workspaces for the operations of add, subtract, rebose and scale
• Updated tests with new class, so any changes to naming conventions will not have tests failing

Description of work:

• The main observable change is the new format of naming workspaces after subtraction
• Instead of the suffix _subtracted, I changed it to include the scaling factor of the background workspace to _minus_ssf_0.95, as seen in:

• 

• Also altered the scaling suffix to match new naming convention

Question

• I altered the tests so that the new class I introduced gets imported into the test and the correct name of the workspace is always used.
• This means that if this class gets changed to include a different naming convention, the tests will continue to pass.
• Is this good practice or should I hard-code the workspace name string into the tests?

To test:

• In the workspace manager, load a workspace and try the arithmetic operations:
  • Scale
  • Subtract
  • Rebose
  • Sum
• Give your opinion on whether the naming convention I implemented makes sense
• Look at the new class WorkspaceNameAppender and tell me if it's fine (maybe needs an initializer method?)
• Look at the location of the new class (under workspaces.helperfunctions), is it the best location or should I move somewhere else?

Fixes #941 .

[GuiMacielPereira]

• Put all workspace name changes into the same class
• The workspace names should not have the character '.' and so I replaced it by '_'
  • (If using the character '.' and produce a script, the script will include a RenameWorkspace algorithm and change the name of the workspace to something weird)
• The prefixes __MSL and __MSLTMP and suffix _HIDDEN are not covered by the tests, so I did a visual test:
  • Followed the following procedure:
    • Load ws MAR21335_Ei60meV
    • Subtract this workspace with itself with some scaling factor
    • Select the subtracted workspace and plot a Slice plot (using default parameters)
    • Check names of workspace in Mantid:
      • These are the same workspaces that appeared before making changes to the code
      • __MSL and _HIDDEN are correctly added to ws names
• The remaining prefixes and suffixes are covered by the tests
  • I checked that altering one of these in the code will cause some tests to fail
  • My new implementation of previous names did not break old tests
• My changes touched files that produce mslice scritps, so I also did a check that all is good with the scripting
  • I followed the procedure described above for the Slice plot and clicked to produce a script
  • The script matches with the script from before the changes (excepting workspace names that are meant to change)
  • Oddly enough, I detected one very small difference that I can't quite understand:
    • The new script uses the Load() function with the argument for Filename as a normal string, whilst the original script before any changes passes this argument as a raw string. I don't think this makes any significant difference.
  • Finally, I tried to run the script I produced on mantid, but this is not possible, as the mslice.cli module does not support the Minus() algorithm (But this is out of scope for this PR)

[GuiMacielPereira]

Altered class to follow Mial's suggestions. As Mial is on his sabbatical, here is the full breakdown of the manual test to perform for someone unfamiliar with this PR:

• Load MAR21335_Ei60meV into mslice

• On the Slice interface, click Display

• These hidden workspaces should appear on the mantid ADS:

• Go to the plot window, and click to generate script to clipboard

• Open a new tab on the mantid editor, paste the script and run it to check it produces the same plot

• Now go back to the mslice interface and click to subtract the ws with itself by some scaling factor:

• A new hidden workspace should appear on the mantid ADS with the suffix _HIDDEN

• Try the other workspace arithmetic operations and check the new naming convention

• Try deleting a workspace in mslice and check it is successfully deleted in the mantid ADS