Problem

Toolbar is not aligned with Headings

Cause

Right now the Y coord of the toolbar is simply a sum of block Y and plugin's padding-top. But a baseline of the text is also depends on the line-height and font-size.

Solution

1. Now we calculate the real baseline of the first input.
2. If block has no inputs or input is far from the top edge (like in Image tool), we use Block Y + padding top, as before.

Resolves #2536