Option to expand rows

[humleflue]

What would you like to be added:
An option to expand rows before taking a screenshot, such that dashboards with collapsed rows can also be screenshotted.

Why is this needed:
If some panels take a long time to load, we have them in a collapsed row by default. Therefore, it would be nice to have the option of expanding panels before taking the screenshot, such that panels within collapsed rows are also included.

Expanding all rows in a dashboard would be a nice first iteration. No need to implement specifying specific rows to expand.