move isolinux to /boot directory to keep cdrom more tidy.

renamed default package list to alpine.packages

Only thing required is a working apk-tools and mkinitfs

init will only autoadd those when booting

the modloop will need loop and cramfs modules. Those are only available
in initramfs stage so we must make sure they are properly loaded.

saves us for lots of headache.

use USBIMG_FREE to set how many kB you want to have as free space on
usb image.

The sda1 might be a sata or scsi harddisk so usb image might be sdb1 or sdc1.
The /dev/usbdisk link will always point to the first usb disk.

The APK_FILES does not contain the dependencies for the wanted packages
so we cannot use this variable when generating the index.

This is so you can build the iso image without having the aports tree.

fixes #28

set default packages dir to ~/packages

I think we only need raid1 and maybe raid5 but now we copy the entire md
subdir. so there are room for size optimization here.

use 'make iso' to build the iso image.

This is because we might want to build for usb