Add video-fit and video-grid-line settings to Video Settings page

[gillamkid]

Before, these 2 settings could only be changed when a MAVLink Camera was connected (editors for the settings exist in the Camera settings page). This was problematic because in some setups there is a video stream but no MAVLink Camera. Adding the settings to the Video Settings page makes so the settings are editable when there is no MAVLink camera.