Implement several properties instead of one showHeader property

[RomanTsukanov]

The header contains different elements:

Customers should be able to control them individually. The API could be as follows:

allowResetAllFilters: true | false, // Shows/hides the Reset Filters button
haveCommercialLicense: true | false, // Shows/hides the watermark

The question selector visibility should depend on the allowHideQuestions property: if it's true, display the selector; if it's false, hide the selector.