OBS Lua SimpleSlides: slide show avoiding the memory limit of Image Slide Show 0.2

Changes

• changed hotkey ids stored in your profile .ini from "slides_reset_button_thingy" to "simpleslides_reset_button" etc. ("thingy" was inherited from the script I used as a base)
• "Reset" action from the script dialog or hotkey now causes the image directory to be rescanned, in case you add or delete files, and then moves to the first slide
• Added code to on_load to initialize any active slideshow (usually has impact only if you reload the script)