docs: refresh & structure overhaul

Rework the doc in order to improve the navigation experience and to make
it easier to update the doc:

- simplify structure: docs/{release-notes,user,developer}
- recreate sphinx config file
- switch theme from opnfv to piccolo
- fix minor rst issues
- fix external references
- add missing license headers (add a short header with copyright and
  SPDX license identifier to the files lacking the information.  The
  header is based on https://github.com/david-a-wheeler/spdx-tutorial)

Change-Id: I9a1135a2873d9955beb26760e0cb6c5d6c1326bd
Signed-off-by: Gwenael Lambrouin <gwenael.lambrouin@orange.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/docs/requirements.txt b/docs/requirements.txt
index 9fde2df..4c9e064 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,2 +1,7 @@
-lfdocs-conf
-sphinx_opnfv_theme
+# Python dependencies needed to build and check nfvbench documentation
+
+sphinx # BSD
+piccolo_theme
+
+# Extract nfvbench version from git
+pbr