Allow quoted strings like --display-name='User One'

[phil-davis]

Description

If we send an occ command fragment like:

--display-name='User One'

Then we do not want to escape it again, because that ends up creating the user with a display name that includes the single quotes literally at each end of the display name.

The work-around is to send:

--display-name 'User One'

But we want to be able to use both ways of writing occ commands, without having to think too much when writing tests.

Checklist:

• Latest changes are published according to instructions in README.md

[phil-davis]

Password policy currently uses this form when doing tests that create users with various passwords.
And we are about to start infrastructure for testing occ commands in core, so the testing app needs to work OK for all "reasonable" forms of occ commands.

[phil-davis]

See issue #36 to add testing for this and other testing app stuff.