[FIRSTBOOT/MAIN] refactor fatresize -s max / LOGs

*) FIRSTBOOT:
- calculate manually "size=max" of MAIN partition (workaround for know bug in libparted ``max_size`` class)
- add debug: write LOG to /mnt/log_firstboot.txt
- ditch "/boot/resize" file method

*)MAIN
- add debug: write LOGS to /mnt/log.txt
- cleanup & use tabs for indendent
- use ${HOME} variable often

*) GENIMAGE
- rm "resize" file (no use)

board/miyoo/genimage-sdcard.cfg

@@ -12,7 +12,6 @@ image bootfs.vfat {
 			"boot/firstboot.custom.sh-OFF",
 			"boot/modules.custom.sh",
 			"boot/normalboot.custom.sh",
-			"boot/resize"
 		}
 		file configs/manifest {
 			image = "boot/configs/manifest"