Update Sphinx version and versioning process

- Updated to newer Sphinx version
- Changed to use doc8 to check .rst files
- Added a dictionary (dict.txt) and spellchecking
- Reformatted and fixed issues that were found in the content

Change-Id: If7b35e01ee8be25dbbd1ecd0e67b264aa6cc2a94
diff --git a/requirements.txt b/requirements.txt
index e4a344f..a65fef2 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,15 +1,15 @@
-Sphinx~=1.8.5
-actdiag~=0.5.4
+Sphinx~=3.1.1
+actdiag~=2.0.0
 blockdiag~=1.5.4
-livereload~=2.6.1
-nwdiag~=1.0.4
+doc8~=0.8.0
+nwdiag~=2.0.0
 recommonmark~=0.6.0
-rstcheck~=3.3.1
-seqdiag~=0.9.6
-sphinx-reload~=0.2.0
+seqdiag~=2.0.0
 sphinx-rtd-theme~=0.4.3
-sphinxcontrib-actdiag~=0.8.5
-sphinxcontrib-blockdiag~=1.5.5
-sphinxcontrib-nwdiag~=0.9.5
-sphinxcontrib-seqdiag~=0.8.5
-git+https://github.com/leokoppel/sphinxcontrib-versioning
+sphinxcontrib-actdiag~=2.0.0
+sphinxcontrib-blockdiag~=2.0.0
+sphinxcontrib-nwdiag~=2.0.0
+sphinxcontrib-openapi~=0.6.0
+sphinxcontrib-seqdiag~=2.0.0
+sphinxcontrib-spelling~=4.3.0
+git+https://github.com/zdw/sphinx-multiversion@ec7c01cdaf2f9241245e84483dfb9bc0d0dffc62