Updating util/README in preparation for the 1.10 release

Broke the previous description of the setchplenv.* scripts into two
sections -- one for quickstart, one for experienced users.

Broke the organization of the README itself into three sections:
novice, experienced user, and developer

Removed mention of the update-sources script, as I think it's time to
retire it (we haven't kept it up-to-date with recent changes and don't
have any sign that it's been used).
Added an entry for build_configs.py; removed update-sources
Fixing indentation
Merge pull request #433 from bradcray/utilImprovementsFor1dot10

Util improvements for 1.10

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