Update git submodules

* Update docs/submodules/qtip from branch 'stable/danube'
  - Add more content to developer overview

    - copy "Coding Style" from `CONTRIBUTING.md`
    - copy "Testing" from `DEVELOP.md`
    - add links of primary packages

    Change-Id: Ia4da2c610a3ceb41ec710904e9437b0449d0a46f
    Signed-off-by: Yujun Zhang <zhang.yujunz@zte.com.cn>
    (cherry picked from commit 540f711b71976c587417b0a3a04a89b79cf465d4)

diff --git a/docs/submodules/qtip b/docs/submodules/qtip
index 4dc621a..88f69a8 160000 (submodule)
--- a/docs/submodules/qtip
+++ b/docs/submodules/qtip
@@ -1 +1 @@
-Subproject commit 4dc621a70a4fcf8e6b2690950be7162fb003cf75
+Subproject commit 88f69a8d9977228a225333f084dc95adc2312f13