Add Pomba submodule

Add logging-analytics/pomba/pomba-audit-common as submodule
Updates to documentation guide

Issue-ID: DOC-323
Change-Id: Ied9363be20c39a893680b07bef964112361c9682
Signed-off-by: Rich Bennett <rb2745@att.com>
(cherry picked from commit 7fc6d943606fbc77d7d9719284bed78d9562ca3b)
diff --git a/.gitmodules b/.gitmodules
index 66de74e..8bed238 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -358,3 +358,8 @@
 	url = ../policy/distribution
 	branch = .
 	ignore = dirty
+[submodule "docs/submodules/logging-analytics/pomba/pomba-audit-common.git"]
+	path = docs/submodules/logging-analytics/pomba/pomba-audit-common.git
+	url = ../logging-analytics/pomba/pomba-audit-common
+	branch = .
+	ignore = dirty