[manta] Fixing flashing for Nexus 10
The current package for the manta can flash the kernel over fastboot but fails on the rootfs because it isn't signed, the current workaround is using the recovery zip installer.
I found out that the manta doesn't care at all about the signature if you flash using heimdall-bootimg instead of fastboot (this device has two bootloaders since its a samsung/nexus thing)
The only problem I have with setting the flashing_method to "heimdall-bootimg" is that that implementation fails flashing at 7% for every partition I try since the images aren't sparse. If I export the rootfs image and run
img2simg on it and then flash the result then the manta should be fully flashable through pmbootstrap