Revise pull request template for better guidance

Ensure that linked issues are actually connected in GitHub and subsequently closed when the PR is merged by prepending the issue number with "Resolves". Also simplifies the formatting.

Author: asbjornu

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,40 +1,49 @@
-<!--- Provide a general summary of your changes in the Title above -->
+<!-- Provide a general summary of your changes in the Title above -->
 
 ## Description
 
-<!--- Describe your changes in detail -->
+<!-- Describe your changes in detail -->
 
 ## Related Issue
 
-<!--- This project only accepts pull requests related to open issues -->
+<!--
 
-<!--- If suggesting a new feature or change, please discuss it in an issue first -->
+This project only accepts pull requests related to open issues.
+If suggesting a new feature or change, please discuss it in an issue first.
+If fixing a bug, there should be an issue describing it with steps to reproduce.
+Please replace "XYZ" below with the issue number that is being resolved by this
+pull request.
 
-<!--- If fixing a bug, there should be an issue describing it with steps to reproduce -->
+-->
 
-<!--- Please link to the issue here: -->
+Resolves #XYZ
 
 ## Motivation and Context
 
-<!--- Why is this change required? What problem does it solve? -->
+<!-- Why is this change required? What problem does it solve? -->
 
 ## How Has This Been Tested?
 
-<!--- Please describe in detail how you tested your changes. -->
+<!-- 
 
-<!--- Include details of your testing environment, and the tests you ran to -->
+Include details of your testing environment, and the tests you ran to
+see how your change affects other areas of the code, etc.
+Please describe in detail how you tested your changes.
 
-<!--- see how your change affects other areas of the code, etc. -->
+-->
 
 ## Screenshots (if appropriate):
 
-<!--- Drag and drop screenshots here -->
+<!-- Drag and drop screenshots here -->
 
 ## Checklist:
 
-<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
+<!--
 
-<!--- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
+Go over all the following points, and put an `x` in all the boxes that apply.
+If you're unsure about any of these, don't hesitate to ask. We're here to help!
+
+-->
 
 * \[ ] My code follows the code style of this project.
 * \[ ] My change requires a change to the documentation.