Adding loops to ui

[MatthiasKainer]

The language already supports loops (see test/public/javascript/src/ast/testLoopParser.ts and test/public/javascript/src/game/compiler/testLoopProcessor.ts), the ui not.

Loop functionality should be added. A first scribble looks like this:

UI

• Add Drag & Drop for so that later items can be added to loop (see Adding drag and drop to program #16 )
• Add action type for loops and scope depth to frontend (see Add action type for loops and scope depth to frontend #20)
• Add nesting to ui

Backend

• Change action triggering from items of program panel getting pulled per timeout and executed from the outside to a script that is created and executed, and notifies the ui from the changes