Util improvements for1dot10

Doing some housecleaning in the util/ directory for the 1.10 release:

* Updated the README to note the quickstart scripts vs. "production" versions
* Sorted the README into beginner / experienced / developer categories
* Added a README entry for build_configs.py which hadn't been noted previously (?)
* Removed the update-sources script, as we have not kept it up-to-date