The `Execute-NUnit` operation is a total disaster in terms of UI/UX:
- rename the operation to `Execute-TestProject` but keep backwards compatibility (i.e. it should be used as `NUnit::Execute-TestProject`)
- fix (or remove) help text to actually be useful, and use placeholder text instead where applicable
- an `$NUnitConsolePath` extension configuration variable should be added to support the path to `nunit-console.exe`
- a path to the NUnit executable should not be required, default to `$NUnitConsolePath`, and should be in Advanced tab
- "Is NUNit v3" property should default to `true` and be moved to Advanced tab
- output directory should automatically be created if specified, default to `$WorkingDirectory` with placeholder text, and not require a surrounding `for directory` block
- capitalization should be correct and consistent