VOL-5132 - Create beta-release branch for voltha-lib-go

VERSION
-------
  o Bump string to latest major.0-dev version to avoid release branch conflicts.

.gitreview
----------
  o Assign defaultbranch=master so release branch problems are easier to detect.

Change-Id: I504a014a881f2595fdbf742c9ce9312f313d6794
diff --git a/.gitreview b/.gitreview
index bf04ac9..b4f747a 100644
--- a/.gitreview
+++ b/.gitreview
@@ -3,3 +3,4 @@
 port=29418
 project=voltha-lib-go.git
 defaultremote=origin
+defaultbranch=master
diff --git a/VERSION b/VERSION
index b3631ba..47244b1 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-7.4.8-dev
+7.5.0-dev