Single remove block input

[DivadNojnarg]

Currently, if we want to remove a block, we click on the block remove button which is input$<stack_ID>_<block_ID>_remove. However, this is not very convenient to handle on the server side since we have to setup many observeEvent (one per button) and this is not ideal when adding new blocks. I would prefer having a single input$<stack_id>_block_remove which holds the index of the block to remove. Ideally, when we click on any remove button, we call Shiny.setInputValue('<stack_id>_block_remove', block_index) in an onclick event. This would allow to get rid of the "last "input changed" workaround.

Let me know what you think @JohnCoene

[JohnCoene]

Yes, we should do that.

[nbenn]

@DivadNojnarg A (semi) related issue might be that of name/ID responsibility: #112

Currently a block ID is a property of the block. Maybe it'd be better to have this be a property of the stack? Something we should discuss.