Remove all warnings during Documentation buildings

Remove all warnings during Documentation buildings

Remove files with not links:
- guides/onap-developer/architecture/blueprint-enr.rst old file based on Beijing
- smsummary.rst: no more relevant as no more submodules used
- templates/sections/vnf-reference.rst : not referenced
- guides/onap-user/onapportal.rst: redundant
- guides/onap-developer/tutorials/index.rst: no tutorial

Add new files to inlude templates
Move templates directory under how-to-use-docs

Modify global release not label with onap_release_notes to avoid confusion

Issue-ID: DOC-692

Signed-off-by: Eric Debeau <eric.debeau@orange.com>
Change-Id: I709765beb02403c4ad058863c2b5136f42968cff
(cherry picked from commit ab0c78bb275b345eb5e995a40a90e633980d7bca)