Add spellcheck and linkcheck exceptions

Add frequently used acronyms or words used in ONAP documentation
Add representative domain or IP addresses are not expected to pass a linkcheck
Add sphinx extension for drawing network diagrams

Change-Id: Iea76f4a279da755fdd5d87e3b723ef261b9d19cd
Issue-ID: DOC-262
Signed-off-by: Rich Bennett <rb2745@att.com>
3 files changed