Add copy / paste scripts

[ego-lay-atman-bay]

This is pretty much the same as my other pull request, but this time it's to the dev branch instead of master, and this time I didn't merge master into it (meaning the only files that were changed are the files I changed (I hope I did it right this time)).

This adds the ability to copy / paste scripts and comments. It works by setting a value to the block xml, which it then loads as if the user dropped a file into the script area. This makes sure that blocks are properly pasted, so if a custom block that doesn't exist in that scene or sprite, it creates the custom block. The only issue with this implementation is that when a user copies a custom block, then changes the custom block and then pastes, the custom block will be replaced by the old definition.

If you right click a block, there will be 3 new options:

• copy below
  • Copy this block and below
• copy block
  • Copy this block only
• cut block
  • Copy this block, and delete it.

Comments also have new options

• copy comment
  • Copy this comment
• cut comment
  • Cut this comment

When you copy a comment, the width is also copies, so when you paste it, it stays the same width.

When you right click the editor area, there is a new option to paste (it only shows if you have already copied something).

There are also some keyboard shortcuts

• ctrl + c - copy all underneath mouse, or if it's a comment, just copy the comment.
• ctrl + shift + c - copy only this block or comment underneath mouse.
• ctrl + x - cut block or comment underneath the mouse.
• ctrl + v - paste whatever is in the clipboard.

I know this would make editing faster, because you don't have to drag blocks a very long distance now. You can just cut the script, then scroll to where you need the script, and paste (and it helps with accidentally dropping it in a c slot while dragging it up or down).

Again, the only issue with this is that when you copy a custom block, edit it, then paste, the definition will revert back to when you copied the block. I don't know of an elegant way of fixing this, as it would require modifying the IDE_Morph.prototype.droppedText function.

I am open to talking about this, and modifications. I don't think it would be best to merge this as it is currently, because I'm not sure if the function names should be renamed.

[ego-lay-atman-bay]

I guess this should continue the discussion at #3280.