[wiki inbox] Firmware image names and formats

Talk about Documentation
#1

Does someone feel like merging these two pages in the inbox
https://openwrt.org/inbox/firmware_image_names
https://openwrt.org/inbox/imageformats

into this one?
https://openwrt.org/docs/techref/image.format

#2

all info now in:
https://openwrt.org/docs/techref/image.format

will check in on it and tidy if no one gets to it.