Split heimdall flash method into heimdall-isorec and heimdall-bootimg

Created by: ollieparanoid

Heimdall is a reverse engineered flasher, that can be used on old Android phones. Right now, we only support the "isorec" method, which means flashing a regular kernel image to the boot/kernel partition and the initramfs to another partition. The kernel contains a minimal initramfs, that will load the second initramfs from the partition, extract it and run it.

In #163 (closed) we found out, that the s762 needs to flash a boot.img file instead of doing this.

heimdall-isorec:

• i9070
• i9100

heimdall-bootimg:

• s7562
• n7100