Do not overwrite title when it is manually set

[madx]

When using WINDOW_TITLE_DYNAMIC, if I set the title for a tab manually it is getting overwritten each time an escape sequence is emitted.

I think the desired behavior is to keep the manually set title, and provide a way to unset it so dynamic title can be enabled again. Maybe setting to an empty title would be fine.

[caleb-]

Added to TODO list.
Ah, I am so lazy recently. :-P