Script-compatible output for list avds and list targets.

Script-compatible output for list avds and list targets.

This adds the following options to the "android"
command line to make it easier to use the outputs
from scripts:

$ android list avds    --compact --null
$ android list targets --compact --null

The short version is '-c -0'.

--compact or -c outputs *justs* the AVD names or the
target identifiers (usable for --target arguments).
with no other information, one per line.

--null or -0 switches EOL from \n to \0, which allows
scripts to process target names with spaces using
xargs -0 or similar.

Change-Id: I18e6ee6b431ed69913a6df37ce34e17ecc721035