Move/add uncrustify documentation to dev manual

Add some basic description of code indentation/formatting guidelines,
and move documentation of uncrustify and related scripts to the
developer manual.  Improve the documentation at the same time, and make
all script reference the developer manual for additional documentation.

Make uncrustify.sh work without explicitly setting the UNCRUSTIFY
environment variable if the pre-commit hook is already configured.

Change-Id: I81ae71fbcdae0e177cc7b05fe278f8c20a19fe7a