Ability to hide the side bar

[bp2008]

Some people want to be able to hide the side bar where PTZ controls are.

To do a good job of this, I need to make several changes:

1. Rename the UI Settings > Top Bar section to Top/Side Bars.
2. Move the system name button setting to that section.
   
3. Add boolean settings to hide the side bar in Live View and in Clips tabs.
4. The system name button should have a new optional action to Toggle Sidebar.
5. Show a visual indicator within the System Name button when the side bar is invisible. Clicking the indicator should open UI Settings, filtered to the appropriate settings.
6. Revise the Top Bar sizing code to not leave blank space for buttons that are not being shown, as this wastes space that could be used by the System Name button at smaller browser widths. (flexbox?)

[bp2008]

Implemented in UI3-269.