Enforce python variable naming conventions for workspace names

[thomashampson]

Description of work

A warning message is displayed whenever a workspace is created with a name that doesn't conformt Python variable naming conventions. This will allow us to move to enforcing this standard in the future.

In debug mode, an exception is raised. This will help avoid any new instances of bad workspace names entering the codebase.

To test:

1. In debug mode, try loading some data using the UI with something invalid in the name field, e.g. with a space in or starting with a number. It should not allow you to load.
2. In release mode, try the same. It should work, but with a warning message in the log. The warning message should appear only once per operation.

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[thomashampson]

I think if we run the tests in debug mode ~200 will fail. We should aim to fix all of that before this is merged to minimise the number of warning messages users will see when running algorithms that internally use bad workspace names.

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[sf1919]

What is happening with this one? It's still in draft. Should we change the milestone?