Rename ServerManager.getSetting to get
Create abstraction for iterating settings
Implement `set(settingsId, value)`

This new public method sets and saves a preference value.
Move settings dialog to its own module

This commit moves all logic for showing the settings
dialog and restart dialog into its own module. In order
to keep things DRY and maintainable the settings
configuration, which contains labels and default values,
has also been moved to its own module.
Substitue <table> with Bootstrap form
Do not use hard-coded value for selector prefix