Various improvements to issue/pull-request templates

- Instruct to verify if an issue/request already exists
- Use uppercase for titles (easier to parse as titles)
- Remove empty lines where it makes sense (instructions)
- Ensure that commit-message appears directly under summary (pull-requests)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,20 +1,17 @@
-##### Issue Type:
-
-<!--- Please pick one and delete the rest: -->
+##### ISSUE TYPE
+<!--- Pick one below and delete the rest: -->
  - Feature Pull Request
  - New Module Pull Request
  - Bugfix Pull Request
  - Docs Pull Request
 
-##### Ansible Version:
-
+##### ANSIBLE VERSION
 ```
-<!--- Paste verbatim output from “ansible --version” here -->
+<!--- Paste verbatim output from “ansible --version” between quotes -->
 ```
 
-##### Summary:
-
-<!--- Please describe the change and the reason for it -->
+##### SUMMARY
+<!--- Describe the change, including rationale and design decisions -->
 
 <!---
 If you are fixing an existing issue, please include "Fixes #nnn" in your
@@ -22,8 +19,6 @@ commit message and your description; but you should still explain what
 the change does.
 -->
 
-##### Example output:
-
 ```
-<!-- Paste verbatim command output here if necessary -->
+<!-- Paste verbatim command output here, e.g. before and after your change -->
 ```