build+ci: switch to python3

Also in this commit:
 * Sync CI scripts with other projects
 * Upgrade waf to version 2.0.19
 * Modernize docs/conf.py
 * Improve README.md and INSTALL.rst

Refs: #5095
Change-Id: Ic0f4f3be07d7266e57d6565a665eb24a757291e8
diff --git a/.jenkins.d/30-coverage.sh b/.jenkins.d/30-coverage.sh
index 9990760..7f8ae58 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 \