In addition to T668 add autotests for:

• original report:script/report:script-interpreter/@text should be saved if script is not modified
• warning should be displayed on opening if report:script/report:script-interpreter/@text is present and interpreter isn't supported
• warning should be displayed on opening if report:script/report:script-interpreter/@text is missing but there are report:item-data-source attributes starting with '=' and interpreter isn't supported
• warning should NOT be displayed on opening if report:script/report:script-interpreter/@text is present or report:item-data-source attributes start with '=' but there is no interpreter set
• warning should be displayed on opening in data mode too (it's missing for now) in the same cases when it's displayed for design mode (see above)
• warning should not be displayed for supported interpreter at all

(for autotests use warnings in a non-visual mode - implement it)