adb: Add a few more wait-for commands

 * wait-for-recovery is obvious.
 * wait-for-online will wait for recovery || device

Change-Id: I70f747bcd201a4157b988d7ed49bcc8e5ff4c85f
Merge pull request #14 from CyanogenMod/cm-10.1

adb: Add a few more wait-for commands