Highlights design

Continuation of #257, just that it is a pull request against development branch. This pull request is addressing #256. Instead of each highlight being one big rectangle area, find smaller reasonable sections and draw border around only them.
All comments must start with a capital and have one space after hash. So change to:
```
# Merge the row
```
This applies to ALL comments in this pull request.
Additionaly, since Merge the row is a title of the section and isn't part of the next line, I'd do one extra line between this and the comment below.