camera: low latency preview and picture

- Take pictures by pressing "s" when the preview opens.
- Depends on sxmo_autorotate.sh
- movie is not currently working. See comments in code
- uses sxiv for image previews of photos taken during that photoshoot
- TODO: use sxiv keyhandlers to add a delete photo function
	- See: /usr/share/examples/sxiv/key-handler
	- I dont know how we would distribute this

scripts/core/sxmo_xinit.sh

@@ -12,6 +12,7 @@ envvars() {
 	[ -z "$XDG_CACHE_HOME" ] && export XDG_CACHE_HOME=~/.cache
 	[ -z "$XDG_DATA_HOME" ] && export XDG_DATA_HOME=~/.local/share
 	[ -z "$XDG_RUNTIME_HOME" ] && export XDG_RUNTIME_HOME=~/.local/run
+	[ -z "$XDG_PICTURES_DIR" ] && export XDG_PICTURES_DIR=~/Pictures
 }
 
 setupxdgruntimedir() {