FS#1408 - Separate device-specific config files in base files & remove white-spaces in bash files

[openwrt-bot]

zhoushiyi213:

The redundant config files for other targets in the same arch (e.g. in /etc/diag.sh, /lib/preinit/, /etc/board.d) can take quite a bit of space (a few of kB after sfs, especially for popular archs like ar71xx). Separating config files into board-specific base-files.ipk packages can be very useful for devices with limited flash space.

Also, it will be much helpful to include an option/script in the image builder for auto-removing comments and white-space in all bash and lua files since this will also be much useful for devices with 4MB flash.