tools: getb64key - print the base64 version of a PEM public key file

Change-Id: Ia94ff560c88dfe85c3fa55db5c8219aa0d3419ee
Store the base64 release key in the OTA zips

This can be directly grepped in pre-existing package.xml tables
to make sure we're not trying to update to a differently signed
build

Change-Id: I7528a8e7c484ea9209cd665b9263328ae834586a
releasetools: Properly handle boot images that use dt
Instead of using a prebuilt boot/recovery image, bring the dt image
into the target files package and use it during package creation

Change-Id: I70ecf74423aad95a3eb8e085029c37450ae354a2

releasetools: don't create prebuilt_dir path if it exits (common.py)
This path may already exists from previous build tasks. Attempting
to create it again will cause an error.

Change-Id: I4baad8bc846470b99f6ce9207c0682401406decc
releasetools: Fix whitespace error for INSTALLED_DTIMAGE_TARGET

Copy/paste produced spaces instead of a tab; fix that

Change-Id: I937e5f6ffd2c947c77dc4baa7427b170c1ea4bcd