Add and refactor tests for features of element "systembars" on a test-site

[annav00]

Add and refactor tests for features of element "systembars" on a test-site:

• [ ] theme (dark/light)
• [ ] height (0-n)
• [ ] lights-out (y/n)
• [ ] window (y/n)
• [ ] getIcons/getIcon(by locator)
• [ ] getText

It has no common properties with other Bars, so it shouldn't be extended from the BasicBar. The class shouldn't contain elements specific to the test site.