PythonScript{,ing} objects are used like file objects for I/O redirect
so need to simulate much of the Python file interface.
Refs #16911

Also adds in missing includes that are now required.

This allows it to closer mimic a file-like object.

Refs #13472

I the algorithm doesn't respond to the cancellation request this
ensures that the script will terminate when returning to Python control.
Refs #13265

Refs #13265

It is only implemented for the Python environment.
Refs #13265

Refs #13080

Refs #9270

Required a small refactor of the code. Hopefully the additional
comments help out.

The inspect.stack() call was failing with a fresh tab because the
executing code didn't have a valid identifier. For a loaded file it
worked because the identifier was automatically set to the filename.

A blank identifier is now not allowed and it uses a default if an
empty string is passed in. This also fixes a bug with the __file__
attribute not being updated on save.

Refs #7076

Packages need to remain only accessible via the package-name.submodule
else it breaks the whole point of them.

Also improved the information you get when one is generated.

Also tidied up the execution code so it's not so cluttered.

Should be temporary as in this case we wouldn't want the output
redirected to the scripting console.
Re #4273.

Variables declared in the script window will now be accessible by
the interpreter and vice versa.

Refs #2854. Should fix occasional crash of interfaces that run python. The interfaces use to populate the autocomplete list even though they don't need to and was causing issues.

Refs #2562 #2556. Should fix problems with scripting window interaction when other things are runnning. The GIL needs aquiring so that Pythn can switch between different running sections, i.e. a Python algorithm from the GUI and a script. Annoying small local changes seems to have had quite an impact.

Update MantidPlot scripting environment to add the path of a script to its sys.path when opened. This fixes the problem with importing modules in the same directory as a open script but outside the Mantid path. Re #1415

MantidPlot scripting autocomplete now inspects objects to update auto complete information after each execution. Required that each tab + the interpreter have different dictionaries so that the autocomplete only sees information 
for the current script. Re #713