Merge branch 'docs-appdev-platform-udpates' into 'master'

Application Development Platform docs updates

See merge request gitlab-org/gitlab-ce!30058

doc/topics/application_development_platform/index.md

 # Application Development Platform
-The GitLab Application Development Platform refers to the set of GitLab features that can be used by operations teams to 
-provide a full development environment to internal software development teams.
+The GitLab Application Development Platform refers to the set of GitLab features used to create, configure, and manage
+a complete software development environment. It provides development, operations, and security teams with a robust feature set aimed at supporting best practices out of the box.
 ## Overview
-The GitLab Application Development Platform aims to reduce and even eliminate the time it takes for an Operations team
-to provide a full environment for software developers. It comprises the following high-level elements:
+The GitLab Application Development Platform aims to:
+
+- Reduce and even eliminate the time it takes for an Operations team
+  to provide a full environment for software developers.
+- Get developers up and running fast so they can focus on writing 
+  great applications with a robust development feature set.
+- Provide best-of-breed security features so that applications developed 
+  with GitLab are not affected by vulnerabilities that may lead to security 
+  problems and unintended use.
+
+It is comprised of the following high-level elements:
 1. Compute
 1. Build, test, and deploy a wide range of applications