Window initial width

[sub07]

2 possibilities:

• letting initial window width. Maybe more natural with some weird window
• force specific width

could be configurable for specific window and for all windows

with a config like default_window_width: inherit OR a percentage of screen width OR a fixed pixel size
initial_window_width: inherit | 50% | 220px

All windows would inherit this value. And could be overridden for specific window