build+ci: switch to python3

Also in this commit:
 * Sync CI scripts with other projects
 * Sync sphinx_build waf tool with ndn-cxx
 * Modernize docs/conf.py
 * Replace redmine_issue extension with sphinx.ext.extlinks
 * Fix typo in docs/doxygen.conf.in
 * Improve README.md

Refs: #5095
Change-Id: Iee05500f907442dd7cb3e41bd613beef7461dab4
diff --git a/.jenkins.d/30-coverage.sh b/.jenkins.d/30-coverage.sh
index a96e999..bb2809d 100755
--- a/.jenkins.d/30-coverage.sh
+++ b/.jenkins.d/30-coverage.sh
@@ -1,10 +1,5 @@
 #!/usr/bin/env bash
-set -e
-
-JDIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
-source "$JDIR"/util.sh
-
-set -x
+set -ex
 
 if [[ $JOB_NAME == *"code-coverage" ]]; then
     gcovr --object-directory=build \
@@ -31,6 +26,6 @@
             --frames \
             --legend \
             --output-directory build/coverage \
-            --title "NDN-NAC unit tests" \
+            --title "ndn-nac unit tests" \
             build/coverage.info
 fi