Add transition for docker recorder preview and update the labeling

This MR is to add most of the additions requested in my previous MR !1293 (merged). This MR will reword the "hold frame" and "result on first frame" options, add toggles to them, and add a transition affect for the "result on first frame" option. The preview transition is a swipe from left to right over 0.5 seconds if at least 1 second is set for the preview duration.

Here is what the new UI will look like:

With the toggles unset:

Tagging @scottpetrovic, @emmetoneill, and @kamathraghavendra since they made these suggestions in the previous MR. @kamathraghavendra if you can, could you give some feedback on the transition affect? Here is an appimage with transition working for the first "MP4 x264" render as profile. If you can let me know if the transition is too fast or slow ( or if you have any other feedback) I would appreciate it 🙂

TODO

• Add transition affect to remaining exporter presets