Fix downssample typo in options

Add interpolation method and weight to merged model output filename

Fix COMMANDINE_ARGS -> COMMANDLINE_ARGS

COMMANDINE_ARGS -> COMMANDLINE_ARGS

Updated `downssample` to `down-sample`, matching spelling in other places.

added console outputs, more clear indication of progress, and ability to specify full filename to checkpoint merger
restore "Loading..." text

Add support for checkpoint merging

adds support for a notification.mp3 in the root directory that will play upon completion (fixes #1013)

ddim_eta & ddim_discretize

refactored image paste handling to fill unset images successively, then replace last existing image (fixes #981)

Fixed grids saving to subdirectory when the setting is unchecked but "save images to subdirectory" was checked.

Fix by @MrAcademy

adds support for a notification.mp3 in the root directory that will play upon completion (fixes #1013)

copy over fields when sending to img2img: https://github.com/AUTOMATIC1111/stable-diffusion-webui/issues/1029