build+ci: switch to python3

Also in this commit:
 * Sync CI scripts with other projects
 * Modernize docs/conf.py
 * Replace redmine_issue extension with sphinx.ext.extlinks
 * Minor updates to docs/doxygen.conf.in
 * Cleanup README.md and INSTALL.rst

Refs: #5095
Change-Id: I614e876e6aed73659f4f4cea01813f4604599263
diff --git a/docs/INSTALL.rst b/docs/INSTALL.rst
index da66e87..f496919 100644
--- a/docs/INSTALL.rst
+++ b/docs/INSTALL.rst
@@ -7,48 +7,36 @@
 Prerequisites
 -------------
 
--  `NFD <https://named-data.net/doc/NFD/>`_ and its requirements:
+-  `NFD <https://named-data.net/doc/NFD/>`_ and its dependencies
 
 Refer to `Getting started with NFD <https://named-data.net/doc/NFD/current/INSTALL.html>`_
 for detailed installation and running instruction.
 
--  ChronoSync library:
+-  ChronoSync library
 
-Download the ChronoSync library and build it according to the instructions at the following
-address:
+Download the ChronoSync library and build it according to the instructions available at
+https://github.com/named-data/ChronoSync#build
 
-   ::
+-  PSync library
 
-       https://github.com/named-data/ChronoSync#build
-
--  PSync library:
-
-Download the PSync library and build it according to the instructions at the following
-address:
-
-   ::
-
-       https://github.com/named-data/PSync#build
+Download the PSync library and build it according to the instructions available at
+https://github.com/named-data/PSync#build
 
 Build
 -----
 
-Execute the following commands to build NLSR:
-
-::
+Execute the following commands to build NLSR::
 
     ./waf configure
     ./waf
     sudo ./waf install
 
-Refer to ``./waf –help`` for more options that can be used during the configure stage and
+Refer to ``./waf --help`` for more options that can be used during the configure stage and
 how to properly configure NLSR.
 
 If your pkgconfig path is not set properly you can do the following before running ``./waf
-configure``
+configure``::
 
-::
-
-    export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig/
-    or
+    export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig
+    # or
     export PKG_CONFIG_PATH=/path/to/pkgconfig/on/your/machine