docs: Add version and build date

Change-Id: I6fd53d3ef12e4b6f1af1e5605c09938bce324ec9
Signed-off-by: jdenisco <jdenisco@cisco.com>

docs/about.rst

@@ -0,0 +1,9 @@
+.. _about:
+
+=====
+About
+=====
+
+**VPP Version:** 19.01-rc0~191-g3206bb1
+
+**Built on:** Tue Nov  6 17:30:04 GMT 2018

docs/index.rst

@@ -29,3 +29,4 @@ Finally it is useful both a software development kit or an appliance out of the
    reference/index
    relatedprojects/index
    archive/index
+   about.rst

docs/scripts/sphinx-make.sh

@@ -8,6 +8,11 @@ then
     pip install -r $DOCS_DIR/etc/requirements.txt
 else
     source $VENV_DIR/bin/activate;
+    VERSION=`source $WS_ROOT/src/scripts/version`
+    TM=`TZ=GMT date`
+    sed -ie "s/**VPP Version:\*\* .*/**VPP Version:** $VERSION/" $DOCS_DIR/about.rst
+    sed -ie "s/**Built on:\*\* .*/**Built on:** $TM/" $DOCS_DIR/about.rst
+    rm $DOCS_DIR/about.rste
     make -C $DOCS_DIR $1
 fi