Line comments should not be treated as separate blocks

[davidbau]

One of the bits of feedback from teachers at CSTA is that code documentations is really important for teaching, and that our block implementation is weak on this.

To improve comments, comments should be attached to the code that they comment.

For example, clicking to the right of a block line of code should allow you to type a comment that would be prefixed by # or // or even <!-- --> in the appropriate language.

Then dragging that block should bring the comment along with it.

The block should not be rendered as if the comment is its own block - the comment should be treated differently than a block for rendering.

The other common position for comments is above lines of code. A comment on its own line (or on multiple lines) immediately above a block should be attached to the block below the comment.