* Makefile - improve/fix check for required make vars
* resolve-profile.py.in
+ build a list of all regions & probe to see which ones are enabled (unknown if special subscription regions like ap-northeast-3 would show up in this list)
+ expand 'ami_regions' 'ALL' meta key to all enabled regions, 'ALL' key's value is preserved (that is, a value of None or False will disable all regions)
+ warn/remove regions in profile config that are found to be disabled.
+ improve checks for [None, False] values
* Build Profiles (completion of PR #49)
+ auto-updates version profile when new release detected
+ updates releases/<profile>.yaml after successful builds
* Prune AMIs (in AWS and in releases/<profile>.yaml
+ 'revision' - keep latest revision per release
+ 'release' - keep latest release per version
+ 'version' - remove end-of-life versions
* releases/README.md updater script
* README overhaul
+ Pre-built AMIs --> releases/README.md
+ profiles/README.md for profile configuration details
+ main README.md overhauled to go over how to build and manage custom AMIs
