build: recovery: Support adding device-specific items

(cdesai): Also add the relevant parts from koush's
commit 7fd5a89df5ec3961c9aedfd2afad50d6d2561056
"Add initial support for charge mode. also support recovery/root in the device tree to easily copy props into recovery images."

Change-Id: I25205e68282680932917016646dabd1abadbfce6
Edify: Add/Update abort messages for some asserts

* If a bootloader or baseband assert is not satisfied, print the
  versions that are supported by the package as well as the version
  on the device.

Change-Id: I958d49281c51bd4e60d596a727bb94cfc4a21909