Dynamic number of rows and columns

[glzbcrt]

Description of the new feature/enhancement

I like to use as much space my resolution allows me, and today it is possible to specify the number of rows and columns. This is great!
However, as I switch between different resolutions I need to keep changing this setting.

In my case I use an external monitor with QHD resolution, but I usually take my notebook to partners and use its own monitor, which doesn't have the same resolution. In this case, when I go from a higher to lower resolution, the terminal is so huge, that I can't even find the settings menu.

Proposed technical implementation details (optional)

Allow the users to specify the number of rows and columns as a percent of the resolution, so each time the terminal is opened it will calculate the number of rows and columns based in the current resolution.