add the functions for multi-stage packages to updater

In order to support multi-stage recovery packages, we add the
set_stage() and get_stage() functions, which store a short string
somewhere it can be accessed across invocations of recovery.  We also
add reboot_now() which updater can invoke to immediately reboot the
device, without doing normal recovery cleanup.  (It can also choose
whether to boot off the boot or recovery partition.)

If the stage string is of the form "#/#", recovery's UI will be
augmented with a simple indicator of what stage you're in, so it
doesn't look like a reboot loop.

Change-Id: I62f7ff0bc802b549c9bcf3cc154a6bad99f94603
Don't abort on read_file if the file is missing.

Change-Id: I85726bf736203d602428114145c3b98692580656
fix unnecessarily slow writing of EMMC partitions

These were attempts to write partitions "conservatively" in hopes of
fixing the problems with writing the radio partition on Nexus 4.  They
didn't work (a kernel patch was needed), but got left in.  They make
writing of partitions unnecessarily slow (ie, we really shouldn't need
to sync() after every 4kb).  Roll back most of them, but leave the
verification read-back in.

Change-Id: I94badc0979e88816c5aa0485f6316c02be69173c
Merge "Don't abort on read_file if the file is missing." into klp-dev
Merge tag 'android-4.4.3_r1.1' into katkiss-4.4

Android 4.4.3 release 1.1